UNIVERSITY  OF  CALIFORNIA 
DEPARTMENT  OF  CIVIL   ENGINEERS 
BERKELEY.  CALIFORNIA 


JIVIL    ENG.     DEPT 


Library 


UMIVERS,TY  OF  CALIFORNIA 

OEPARTMENT  OF  ClVtU  ENG.NEER.NG 

BERKELEY.  CALIFORNIA 


HIGHWAY 
ENGINEERING 


BY 

CHAS.  E.  MORRISON,  A.M.,  C.E. 

Tutor  in  Civil  Engineering,   Columbia  University 


FIRST    EDITION 
FIRST  THOUSAND 


NEW  YORK: 

JOHN   WILEY  &  SONS 

LONDON:    CHAPMAN  &  HALL,  LIMITED 
1908 


Engineering 
Library 


COPYRIGHT,   1908, 
BY  CHAS.   E.  MORRISON 


PRESS   OF    THE    PUBLISHERS    PRINTING    COMPANY,    NEW    YORK,    U.  S.  A. 


PREFACE 

THE  following  pages  were  prepared  for  the  second-year 
students  of  the  department  of  civil  engineering  at  Columbia 
University,  with  a  view  to  furnishing  a  text  in  which  the  funda- 
mentals of  the  subject  should  not  be  buried  in  a  mass  of  de- 
tail, such  as  is  frequently  found  to  be  the  case  in  works  of  a 
similar  character. 

This  book  is,  therefore,  not  a  reference-work,  but  rather  one 
in  which  it  has  been  the  endeavor  to  outline  and  emphasize 
those  basic  principles  which  are  essential  to  good  highways. 

Acknowledgment  is  here  made  for  the  assistance  that  has 
been  obtained  from  the  many  excellent  works  on  the  subject, 
and  from  the  Government  and  State  reports.  In  a  number  of 
cases  these  have  been  quoted  from  quite  freely. 

COLUMBIA  UNIVERSITY,  August,  1908. 


in 


442229 


CONTENTS 


PAGE 

CHAPTER  I 
ROAD  RESISTANCES    .       »      .^       . 1 

CHAPTER  II 
EARTH  ROADS 24 

CHAPTER  III 
GRAVEL  ROADS  .        . 64 

CHAPTER  IV 
BROKEN-STONE  ROADS 70 

CHAPTER  V 
MISCELLANEOUS  ROADS 143 

CHAPTER  VI 
STREET  DESIGN  .  156 

CHAPTER  VII 
STONE  PAVEMENTS 176 

CHAPTER  VIII 
BRICK  PAVEMENTS    .         .       .       .        .  - 194 

CHAPTER  IX 
ASPHALT  PAVEMENTS  .  222 


CHAPTER  X 

MODERN  WOODEN  PAVEMENTS         .        .  .  273 


HIGHWAY  ENGINEERING 


CHAPTER  I 
ROAD   RESISTANCES 

SINCE  in  transportation  of  any  kind,  whether  by  means  of  cars 
as  on  railways,  or  wagons  as  on  ordinary  roads,  the  object  is  to 
haul  a  load  as  cheaply  as  possible — that  is,  aside  from  the  questions 
of  initial  cost  and  maintenance  and  repair,  to  haul  the  greatest 
load  with  the  least  expenditure  of  energy — it  will  be  quite  proper 
in  the  subject  of  roads  arid  pavements  to  consider  first  those 
factors  tending  to  affect  the  tractive  force  per  unit  load  and 
thus  the  cost  of  transportation. 

By  tractive  force  is  meant  the  force  exerted  by  a  team  in 
drawing  a  load  over  a  road,  and  it  is  usually  expressed  in  pounds 
per  ton.  The  resistances  to  be  overcome,  called  tractive  re- 
sistances, are  due  to  the  load  itself  and  the  wagon  carrying  it. 
The  general  term  tractive  resistance,  as  applied  to  wagon  haul- 
age, may  be  separated  into  three  parts:  (1)  Axle  friction,  (2) 
Rolling  resistance,  and  (3)  Grade  resistance;  and  from  this  con- 
sideration the  most  advantageous  condition  of  road  transporta- 
tion may  be  determined. 

Axle  Friction.  Not  very  much  is  definitely  known  concern- 
ing this  factor  in  wagon  haulage,  not  only  because  of  the  few  ex- 
periments made  for  its  determination,  but  because  of  its  rela- 
tively small  importance  as  compared  with  the  other  resistances. 

i 


$e.  ''"*.    HIGHWAY   ENGINEERING 

Those  experiments  that  have  been  made,  however,  seem  to  check 
fairly  well  similar  values  obtained  with  railway  car  journals  and 
in  machines. 

Axle  friction  depends  upon  the  nature  of  the  rubbing  surfaces, 
i.e.,  the  material  of  which  the  hub  and  axle  are  made,  upon  the 
degree  of  lubrication,  and  the  nature  of  the  lubricant.  With  poor 
lubrication,  this  factor  will  be  from  two  to  six  times  the  value 
obtained  with  good  lubrication.  In  car  journals,  at  least,  the 
axle  friction  is  dependent  to  some  extent  upon  both  velocity  and 
temperature.  That  it  varies  inversely  as  some  function  of  the 
pressure  is  known,  but  the  exact  relation  has  never  been  deter- 
mined. According  to  Baker,  for  light  carriages  when  loaded,  the 
coefficient  of  friction  is  about  0.020  of  the  weight  on  the  axle,  for 
heavier  carriages  0.015,  and  for  common  American  wagons  0.012; 
or  for  the  above  carriages,  from  3  to  4J  Ibs.  of  tractive  force  per 
ton  of  weight  on  the  axle  may  be  charged  to  axle  friction.  As  the 
diameter  of  the  axle  is  decreased,  and  that  of  the  wheel  increased, 
the  friction  resistance  may  be  diminished,  but  it  should  be  ob- 
served that  an  undue  decrease  in  the  cross-section  of  the  axle 
increases  the  axle  pressure  per  unit  area,  causing  excessive  heat 
and  wear. 

In  train  resistances,  the  coefficient  of  resistance,  in  pounds  per 
ton  due  to  axle  friction,  has  been  found  to  be  equal  to  the  product 
of  the  coefficient  of  friction  times  the  diameter  of  the  axle,  divided 
by  the  diameter  of  the  wheel,  multiplied  by  the  number  of  pounds 
in  a  ton. 


Coefficient  of  resistance  = 

coefficient  of  friction  X  diameter  of  axle 


X  2,000 


diameter  of  wheel 

Rolling  Resistance.  This  is  made  up  of  several  components 
but  is  due  principally  to  the  fact  that,  no  matter  how  perfect 
the  road's  surface,  the  wheel  of  a  vehicle  will  always  sink  to  some 
extent  into  the  metal,  and  it  is  thus  always  in  the  act  of  rolling 


ROAD   RESISTANCES  3 

up  a  small  incline.  This  of  course  is  less  in  the  case  of  the 
wheels  of  a  locomotive  on  steel  rails  than  in  that  of  an  ordinary 
cart  hauled  over  an  average  road,  but  it  exists  in  the  former  as 
well  as  in  the  latter. 

The  tractive  force  required  to  overcome  this  resistance  might 
be  found  by  the  following  demonstration.     In  Fig.  1,  let  VDR  be 


the  original  and  natural  surface  of  the  road,  0  the  centre  of  the 
wheel  ZYD,  TY  the  depth  to  which  the  wheel  has  sunk  into  the 
road  metal,  and  P  the  direction  of  the  motive  force. 

The  submerged  portion  of  the  wheel  is  DY,  of  which  it  may 
be  assumed  that  the  arc  corresponds  with  the  chord.  The  re- 
sistance to  penetration  then  is  a  maximum  at  Y,  zero  at  D, 
diminishing  with  the  depth  of  depression,  and  maybe  represented 
by  an  isosceles  triangle  with  the  centre  of  gravity  at  N,  located 
one-third  the  distance  YN  from  the  base  Y.  This  is  also  the 
centre  of  resistance  and  pressure  of  the  load  measured  in  direc- 
tion and  intensity  by  OS.  The  tractive  force  is  measured  by 
NS  or  MO.  Since  the  depth  TY  is  small,  OS  may  be  assumed 
equal  to  the  radius  of  the  wheel  OY,  and  NS  as  one-third  of  the 
one-half  chord  DT.  It  follows  then  that  if  W=the  load,  T.F.  = 
the  tractive  force,  and  R= radius  of  wheel, 


HIGHWAY  ENGINEERING 


W:T.F.  ::OY:        :  :R:-( 


DT  DT 

^i  :  :R:-( 

o  o 


and 


W  X 


DT 


the  resistance  to  traction  = 


but 

DT=  V  ZT  x  TY 
and  therefore  the  tractive  force, 

M0=—      W  ^  ZT  x  TY 
3  R 

On  the  other  hand,  the  power  required  to  draw  a  wheel  over 
an  obstacle  such  as  a  stone  may  be  determined  as  follows. 
Let  0  be  the  centre  of  the  wheel,  YZ  the  road,  S  the  obstacle, 
and  P  the  direction  of  the  motive  force  OM.  This  is  the  force 
necessary  to  draw  the  wheel  to  the  point  S.  The  moment  of  the 


FIG.  2. 

tractive  force  is  equal  to  the  force  OM  times  its  lever  arm  MS. 
But  the  weight  of  the  load  is  acting  in  the  direction  OY  and  is 
represented  in  intensity  by  OX;  its  lever  arm  is  therefore  equal 
to  XS.  For  a  condition  of  equilibrium  XS  X  OX  =  OM  X  MS.  If 
OM  be  represented  by  P  and  OX  by  W,  then  the  tractive  force 

P_  W— 

~  WMS 


EOAD  RESISTANCES  5 

The  various  components  of  rolling  resistance  affecting  its 
value  are  :  (a)  The  diameter  of  the  wheel  ;  (b)  The  width  of  the 
tire;  (c)  The  speed;  (d)  The  presence  or  absence  of  springs,  and 
(e)  The  road  surface. 

THE  DIAMETER  OF  THE  WHEEL.  Experimentally  it  has  been 
determined  that  the  diameter  of  a  wheel  affects  the  rolling  re- 
sistance in  some  inverse  ratio.  This  may  be  accounted  for  by 
the  fact  that  the  smaller  wheel  makes  a  deeper  depression  in  a 
road  than  the  larger,  and  therefore  requires  greater  effort  to  haul 
it  out.  The  previous  figure  gives  the  following  solution  : 

vo 

P  X  MS  =  W  X  XS  or  P  =  W 


XS  :  MS  :  :  tan  XOS  :  1     (dividing  by  MS) 
tan  XOS  =  tan  2(SYZ) 
.'.P  =  Wtan2(SYZ) 

But  as  the  SYZ  increases  inversely  as  the  diameter  of  the  wheel, 
the  value  of  P  will  vary  in  like  manner,  and  large  wheels  are  hence 
better  than  small  ones. 

M.  Morin  experimenting  upon  the  effect  of  diameter  found 
that  on  a  given  road  and  with  a  given  load,  a  6  ft.  8  in.  wheel  had 
but  little  effect  upon  the  road  surface;  that  a  4  ft.  9  in.  wheel  cut 
deep  ruts,  and  that  a  10.5  in.  wheel  cut  still  deeper  ruts. 

At  Bedford,  England,  in  1874,  it  was  shown  what  effect  the 
diameter  of  a  wheel  exerted  upon  the  tractive  force,  when  it  was 
demonstrated  that  a  pull  of  1  Ib.  could  move  a  load  of  35.1  Ibs. 
resting  on  a  wheel  3  ft.  5  ins.  in  diameter,  whereas  the  same  force 
could  move  as  much  as  58.7  Ibs.  on  a  wheel  5.0  ft.  in  diameter. 

Naturally  the  smaller  wheels  present  the  smaller  bearing  sur- 
face to  the  road,  thus  increasing  the  pressure  per  unit  area  for 
equally  weighted  vehicles.  This  increase  frequently  causes  the 
depressions  in,  and  undue  wear  of,  the  road's  surface. 

THE  WIDTH  OF  TIRE.  Perhaps  no  one  of  the  above-men- 
tioned components  of  rolling  resistance  has  been  discussed  so 
frequently  and  so  much  as  that  of  width  of  tire,  in  its  effect  upon 


6  HIGHWAY   ENGINEERING 

both  haulage  and  road  preservation.  Generally  the  subject  is 
approached  from  the  standpoint  of  road  preservation  rather  than 
that  of  decrease  in  tractive  force ;  but  both  are  worthy  of  care- 
ful consideration. 

Narrow-tired  wheels,  like  those  of  small  diameter,  are  fre- 
quently required  to  carry  a  greater  load  per  unit  of  bearing  sur- 
face than  is  desirable,  with  the  consequent  effect  that  they  not 
only  increase  the  effort  upon  the  horse,  but,  sinking  deeper  into 
the  road,  tend  to  destroy  it  more  quickly. 

Though  it  is  generally  considered  that  the  adoption  and  use  of 
broad  tires  will  improve  the  road  surface,  the  fact  was  mentioned 
by  the  Massachusetts  State  Highway  Commission,  in  its  Report  of 
1893,  that  results  might  not  warrant  such  a  change.  Assuming 
that  in  the  State  of  Massachusetts  there  were  50,000  vehicles 
requiring  a  change  in  the  width  of  tire,  at  an  average  cost  of  $20  a 
vehicle,  this  would  mean  an  expenditure  of  $1,000,000  for  the 
alteration.  It  was  pointed  out  that  with  this  amount  200  miles 
of  very  excellent  road  could  be  built  "  of  the  kind  that  would  not 
be  affected  by  any  width  of  tire."  This  is  a  point  well  taken,  but 
it  should  be  remembered  that  varying  conditions  require  different 
consideration. 

In  New  Jersey  it  is  maintained  by  the  Highway  Commission 
that  when  a  road  is  improved,  immediately  heavier  loads  are 
hauled  on  the  same  tires,  causing  ruts  which  hold  water,  with  the 
consequent  result  of  the  disintegration  of  the  foundation.  Such  ill 
effects  can  only  be  overcome  by  wider  tires,  thus  decreasing  the 
unit  load  and  the  destructive  effects  of  the  wheels.  It  has  also 
been  suggested  that  to  supplement  the  good  effect  of  road-rolling 
machines,  four-inch  tires  be  required  on  heavy  trucks  and  that 
their  owner's  license  be  denied  until  such  requirements  be  com- 
plied with. 

To  this  effect,  an  act  of  the  New  Jersey  Legislature  dated 
March  24th,  1896,  permits  township  committees  to  pass  an  ordi- 
nance allowing  a  rebate  of  taxes  to  owners  or  possessors  of  wagons 


ROAD   RESISTANCES  7 

and  carts  with  tires  not  less  than  four  inches  in  width;  and  in 
Maryland,  on  toll  roads,  only  one-half  the  rate  is  collected  from 
drivers  of  broad-tired  wagons. 

Experiments  show  that  with  a  uniform  load  and  wheels  of 
equal  diameter,  a  tire  2.4  inches  causes  double  the  wear  to  the 
road  that  is  produced  by  a  tire  4.6  inches  wide;  but  it  may  be 
questioned  if  tires  broader  than  this  have  any  advantage. 

Tests  made  at  the  Missouri  Experiment  Station  covering  a 
period  of  two  years,  on  macadam,  gravel,  and  dirt  roads,  in  all 
conditions,  and  on  meadow,  pasture,  and  ploughed  land,  both 
wet  and  dry,  show  the  following  results.  The  tests  were  made 
with  a  net  load  of  2,000  pounds  in  every  case,  a  self-recording 
dynamometer  being  used  to  measure  the  tractive  force. 

"  1.  ON  MACADAM  STREET.  As  an  average  of  2  trials  made,  a 
load  of  2,518  Ibs.  could  have  been  hauled  on  the  broad  tires  (6 
ins.)  with  the  same  draught  that  a  load  of  2,000  Ibs.  required 
on  narrow  tires  (1J  ins.). 

"2.  GRAVEL  ROAD.  In  all  conditions  of  the  gravel  road, 
except  wet  and  sloppy  on  top,  the  draught  of  the  broad-tired 
wagon  was  very  much  less  than  that  of  the  narrow-tired  wagon. 
Averaging  the  6  trials,  a  load  of  2,482  Ibs.  could  be  hauled  on 
the  broad  tires  with  the  same  draught  required  for  a  load  of 
2,000  Ibs.  on  the  narrow  tires. 

"  3.  DIRT  ROAD,  (a)  When  dry,  hard,  and  free  from  ruts  and 
dust,  2,530  Ibs.  could  have  been  hauled  on  the  broad  tires  with  the 
same  draught  required  for  2,000  Ibs.  on  the  narrow  tires,  (b) 
When  the  surface  was  covered  with  2  or  3  ins.  of  very  dry  loose 
dust,  the  results  were  unfavorable  to  the  broad  tire.  The  dust 
on  the  road  in  each  of  these  trials  was  unusually  deep,  (c)  On 
clay  road,  muddy  and  sticky  on  the  surface  and  firm  underneath, 
the  results  were  uniformly  unfavorable  to  the  broad  tires,  (d) 
On  clay  road,  with  mud  deep  and  drying  on  top,  or  dry  on  top 
and  spongy  underneath,  a  large  number  of  tests  showed  uni- 
formly favorable  to  the  broad  tire.  The  difference  amounted  to 


8  HIGHWAY  ENGINEERING 

from  52  to  61  per  cent,  or  about  3,200  Ibs.  could  have  been 
hauled  on  the  broad  tires  with  the  same  draught  required  to 
draw  2,000  Ibs.  on  the  narrow  tires.  In  this  condition  of  road 
the  broad  tires  show  to  their  greatest  advantage.  As  the  road 
dries  and  becomes  firmer,  the  difference  of  the  draught  of  the 
broad  and  narrow  tires  gradually  diminishes  until  it  reaches 
about  25  to  30  per  cent  on  dry,  level,  smooth  dirt,  gravel,  or 
macadam  road  in  favor  of  the  broad  tire.  On  the  other  hand, 
as  the  mud  becomes  softer  and  deeper,  the  difference  between 
the  draught  of  the  two  types  of  wagons  rapidly  diminishes  until 
the  condition  is  reached  when  the  mud  adheres  to  both  sets  of 
wheels;  here  the  advantage  of  the  broad  tires  ceases  entirely, 
and  the  narrow  tires  pull  materially  lighter,  (e)  Clay  road, 
surface  dry,  with  deep  ruts  cut  by  narrow  tires  in  the  ordinary 
use  of  the  road.  In  every  trial  the  first  run  of  the  broad  tire 
over  the  narrow-tire  ruts  showed  a  materially  increased  draught 
when  compared  with  that  of  the  narrow  tire  run  in  its  own 
rut.  The  second  run  of  the  broad  tires  in  the  same  track, 
where  the  rut  is  not  deep,  completely  eliminated  this  disad- 
vantage, and  showed  a  lighter  draught  for  the  broad  tire  than 
the  narrow  tire  showed  in  the  first  run.  Where  the  ruts  were 
eight  inches  deep,  with  rigid  walls,  three  runs  of  the  broad  tire 
in  its  own  track  over  the  ruts  were  required  to  eliminate  the 
disadvantage.  Three  runs  of  the  broad  tire  over  this  track 
have  in  all  cases  been  sufficient,  however,  to  so  improve  the 
road  surface  that  both  the  broad-  and  narrow-tired  wagons 
passed  over  this  road  with  less  draught  than  the  narrow  tires  did 
in  the  original  ruts.  In  addition  to  the  saving  of  draught,  the 
road  was  made  very  much  more  comfortable  and  pleasant  for  the 
users  of  light  vehicles  and  pleasure  carriages  by  the  few  runs  of 
the  six-inch  tire.  Summing  up  all  the  tests  on  dirt  roads,  it  ap- 
pears that  there  are  but  three  conditions  on  which  the  broad  tires 
draw  heavier  than  the  narrow  tires,  namely,  (1)  When  the  road 
is  sloppy,  muddy  or  sticky  on  the  surface,  and  firm  or  hard  under- 


ROAD   RESISTANCES  9 

neath;  (2)  when  the  surface  is  covered  with  a  very  deep,  loose 
dust,  and  hard  underneath;  (3)  when  the  mud  is  very  deep  and 
so  sticky  that  it  adheres  to  the  wheels  on  both  kinds  of  wagons. 
It  appears  that  the  dust  must  be  extraordinarily  deep  to  show  a 
higher  draught  from  the  broad  tires  than  from  the  narrow  tires. 
The  three  conditions  just  named,  therefore,  are  somewhat  un- 
usual and  of  comparatively  short  duration.  Through  a  majority 
of  days  in  the  year,  and  at  times  when  the  dirt  roads  are  most 
used,  and  when  their  use  is  most  imperative,  the  broad-tired 
wagons  pull  materially  lighter  than  the  narrow-tired  wagons. 

"  4.  A  large  number  of  tests  on  meadow,  pasture,  and  stubble- 
land,  corn  ground  and  ploughed  ground  in  every  condition,  from 
dry,  hard,  and  firm  to  wet  and  soft,  show  without  a  single  excep- 
tion a  large  difference  in  draught  in  favor  of  the  broad  tires. 
This  difference  ranged  from  17  to  120  per  cent. 

"  5.  It  appears  that  6  ins.  is  the  best  width  of  tire  for  a  com- 
bination farm  and  road  wagon,  and  that  both  axles  should  be 
the  same  length,  so  that  the  front  and  hind  wheels  will  run  in 
the  same  track." 

It  is  therefore  evident  that  wide  tires  not  only  tend  to  di- 
minish the  draught  under  most  conditions,  but  that  they  also 
aid  in  the  preservation  of  the  road  surface. 

SPEED  increases  the  rolling  resistance,  as  the  shocks,  due  to 
irregularities  in  the  surface,  occur  with  greater  frequency.  On  a 
uniformly  smooth  surface,  MM.  Morin  and  Dupuit  found  that  the 
resistance  to  traction  is  independent  of  the  speed,  but  on  ordinary 
roads  or  pavements  it  has  been  shown  to  vary  as  some  power  of 
the  velocity.  Naturally  it  is  dependent  upon  the  surface  and 
also  upon  the  presence  or  absence  of  springs. 

SPRINGS  decrease  the  shock  to  which  the  vehicle  is  subject  in 
rolling  over  rough  surfaces,  and  hence  diminish  the  tractive  force 
as  well  as  wear  and  tear  to  wagon  and  road.  For  smooth  roads, 
this  will  vary  less  than  for  rough.  Like  speed,  it  is  but  a  small 
factor  in  rolling  resistance. 

ROAD  SURFACE.    The  effect  of  the  road  surface  upon  rolling 


10 


HIGHWAY  ENGINEERING 


resistance  and  tractive  force  is  quite  evident  in  the  two  extreme 
cases  of  a  railway  and  an  ordinary  dirt  road.  It  requires  no 
demonstration  to  be  convinced  that  for  the  same  expenditure  of 
energy,  other  things  being  equal,  a  very  much  heavier  load  may 
be  hauled  on  the  former  than  on  the  latter.  In  other  words,  the 
smoother  and  harder  the  road  for  a  level  surface,  and  disregard- 
ing the  question  of  foothold,  the  greater  the  load  that  may  be 
hauled  for  a  unit  of  power.  Smoothness  and  hardness  not  only 
reduce  tractive  force,  but  produce  comfort,  and  diminish  shock, 
wear  and  tear  on  road,  vehicle,  and  animal. 

The  following  figure  represents  graphically  the  conditions 
resulting  from  various  pavements. 


10  HORSES 
ON  LOOSE  SAND 
.      OR  MUD  ROAD 


Ys  HORSE  ON 

IRON  PLATES 

OR  RAILS 


FIG.  3.— Showing  the  Effect  of  Road  Covering  on  Tractive  Force. 
As  showing  the  effect  of  surface  upon  tractive  force,  the  fol- 
lowing table  from  Sir  John  McNeill  is  given : 


Tractive  Force. 
Pounds  Per  Ton. 


Kind  of  Koad. 

Well-made  block  pavement 33 

Telf ord  or  macadam 46 

Old  flint  road 65 

Loose  gravel 147 


ROAD   RESISTANCES 


11 


The  results  tabulated  below  are  from  the  tests  made  by  M. 
Morin : 


TRACTIV 

E  FORCE. 

Kind  of  Road. 

Carts,  3  Miles 
per  Hour. 
Pounds  per 
Ton. 

Wagons  2  Tons, 
3  Miles  per 
Hour. 
Pounds  per 

Carriages  with 
Springs, 
3  Miles  per 
Hour. 
Pounds  per 

Carriages  with 
Springs, 
6  Miles  per 
Hour. 
Pounds  per 

Ton. 

Ton. 

New  road  with  5  ins.  of 

gravel  .  .  

166 

222 

250 

Earth  road  with  £  in.  of 

gravel  

125 

191 

200 

Broken    stone    in    best 

condition  

27 

37 

42 

48 

Broken  stone,  much  rut- 

ted and  very  muddy  .  . 
Pavement,  clean 

105 
11 

143 
30 

166 
35 

200 
53 

Pavement,  muddy  

14 

40 

45 

66 

The  following  table  from  Rudolph  Herring  shows  the  effect  of 
road  surface  on  tractive  force.  The  velocity  in  each  case  is  three 
miles  per  hour. 


Kind  of  Road. 

Loose  sand 448 

Loose  gravel  (deep) 320 

Loose  gravel  (4  ins.) 222 

Common  gravel  road 147 

Good  gravel 88 

Hard  rolled  gravel 75 

Ordinary  dirt  road 224 

Hard  clay 112 

Hard,  dry,  dirt  road 89 

Macadam,  little  used 140  to    97 

Bad  macadam 160 

Poor  macadam 112 

Common  macadam 64 

Good  macadam,  wet 75  to  42 

Best  French  macadam 45 

Very  hard  and  smooth  macadam 46 


Tractive  Force. 

Pounds.          Authority. 

Bevan. 

Morin. 
McNeill. 
Rumford. 
Minard. 

Bevan. 
(i 

Morin. 

Gordon. 

Navier. 

Peidounet. 

Morin. 

Navier. 

McNeill. 


12  HIGHWAY  ENGINEERING 

Tractive  Force. 

Kind  of  Road.  Pounds.  Authority. 

Best  macadam  ....................  50  Rumford. 

...................  49  to  37£  Gordon. 

Best  macadam  ...................  52  to  32  Morin. 

Cobblestone,  ordinary  ..............  140  Kossack. 

Cobblestone,  good  .................  75              " 

Belgian  block  .....................  56  McNeill. 

Belgian  block  in  Paris  ............  ".  54  to    34  Navier. 

Belgian  block  .....................  37£  Rumford. 

Belgian  block,  good  ................  34£  McNeill. 

Belgian  block  .....................  50  to    26  Morin. 

Stone  block,  ordinary  ..............  90  Minard. 

Stone  block,  good  .................  45  Rumford 

Stone  block,  London  ...............  36  Gordon. 

Asphalt  ..........................  17 

Granite  tramway  ..................  13£            " 


Iron  railway  ......................  11£  " 

....................  8         Lecount. 

The  results  of  traction  tests  given  below  were  made  by  the 
Office  of  Road  Inquiry  of  the  U.  S.  Government. 

Tractive  Force. 
Kind  of  Road.  Pounds. 

Loose  sand  (experimental)  .............................  320 

Best  gravel  (park  road)  ...............................  51 

Best  clay  ............................................  98 

Best  macadam  .......................................  38 

Poor  block  pavement  .................................  42 

Cobblestone  ..........................................  54 

Poor  asphalt  .........................................  26 

In  the  line  of  relative  tractive  resistance  on  brick  and 
asphalt  pavements  few  tests  have  vet  been  made,  so  that 
the  following  results  obtained  from  'tests  made  by  the  De- 
partment of  Civil  Engineering  of  Iowa  State  University  are 
of  some  value. 


ROAD   RESISTANCES  13 


TRACTION  TESTS  ON  BRICK  AND  ASPHALT  PAVEMENTS. 

Tractive  Resistance. 
Character  of  Pavements.  Pounds  per  Ton. 

Brick  Pavement 

One  course,  sand-filled,  much  worn  and  broken 58 

On  concrete,  sand-filled,  much  worn  and  rough 43 . 3 

Same  as  above 37 . 6 

On  concrete,  sand-filled,  dirty,  well  worn 33.3 

On  concrete,  nearly  new,  cement-filled 31 .7 

On  sand,  sand-filled,  condition  fair 29 . 1 

New,  sand-filled 37.2 

Old,  tar-filled,  smooth,  clean 28 . 2 

Old,  cement-filled,  clean,  smooth 25.4 

Clean 16 

Dirty 19 

Asphalt  Pavement. 

New,  quite  dirty 26  7 

New,  clean,  smooth 24 . 0 

New,  clean,  smooth 23 . 3 

Old,  clean,  much  used 29 . 1 

New,  clean,  little  used 24 . 2 

Old,  dirty,  little  used 39 . 9 

Old,  clean,  very  little  used,  pitted 67 . 8 

Same  as  above,  but  colder 36 . 5 

Same  as  above  after  period  of  cold  weather,  dirty 34 . 4 

Clean,  new,  very  little  used 55 . 5 

Same  as  above,  but  colder 31.1 

Same  as  above  after  period  of  cold  weather,  fairly  clean 26 . 5 

Block  asphalt,  one  year  old,  much  used,  worn,  clean 28 

Clean 34 

The  above  were  all  made  with  ordinary  draught  wagons. 

TRACTION  TESTS.  The  determination  of  values  such  as  given 
above  constitutes  what  is  known  as  a  traction  test.  Various  in- 
struments have  been  used  to  measure  the  amount  of  effort  ex- 
erted by  a  horse  in  hauling  a  load  over  a  road,  with  the  object  of 
learning  which  pavement  permits  of  the  largest  load,  and  hence 
gives  the  cheapest  cost  of  transportation. 

In  road  construction,  as  in  every  other  branch  of  engineering, 
it  should  be  remembered  that  the  question  of  cost  is  important — 


14  HIGHWAY  ENGINEERING 

if  not  the  most  important — and  that  good  roads  are  represented 
by  those  over  which  loads  may  be  transported  for  the  least  ex- 
penditure. To  compare  the  cost  of  haulage  it  therefore  becomes 
necessary  to  determine  the  effort  exerted.  The  pioneers  and 
authorities  along  this  line  were  M.  Morin,  who  experimented  for 
the  French  government,  and  Sir  John  McNeill  in  England.  The 
latter's  results  were  published  in  1848,  while  the  former's  ap- 
peared in  1843. 

The  more  recent  results  of  the  experiments  of  the  Department 
of  Agriculture,  made  in  1895,  are  of  distinct  value.  They  were 
made  on  the  roads  of  the  United  States  Road  Exhibit  at  the 
Cotton  States  and  International  Exposition  in  Atlanta,  Ga.,  in 
1895.  The  wagon  and  load  were  similar  to  those  in  daily  use  in 
the  Southern  States  to  demonstrate  to  the  public  the  advantage 
of  improved  roads.  Three  kinds  of  roads  were  used,  a  modern 
macadam,  a  sand  road,  and  an  ordinary  dirt  road,  the  latter  two 
being  types  of  the  more  common  roads  in  the  South. 

The  macadam  road  was  300  ft.  long,  made  up  of  six  50  ft. 
sections,  varying  in  rise  by  2  per  cent  increments,  from  a  level 
to  a  grade  of  10  per  cent.  The  sand  and  the  dirt  roads  were  each 
200  ft.  long,  divided  into  50  ft.  sections,  varying  in  a  similar 
manner  from  a  level  to  a  grade  of  6  per  cent.  The  tests  therefore 
show  the  results  not  only  of  road  surface,  but  grade  as  well. 

The  macadam  road,  12  ft.  wide,  had  a  natural  clay  subgrade, 
which  was  well  rolled.  On  top  of  this  4  ins.  of  2  in.  blue  Trenton 
limestone  was  placed,  followed  by  a  course  of  2  in.  screenings, 
each  being  subjected  to  the  action  of  a  road  roller. 

The  sand  road  was  12  ft.  wide  also,  consisting  of  6  ins.  of 
river  sand  placed  on  a  bed  of  natural  clay,  neither  the  bed  nor  the 
surface  being  rolled. 

The  dirt  road  was  made  of  natural  earth.  To  approximate 
general  conditions,  it  was  thoroughly  wetted  and  had  a  heavily 
laden  narrow-tired  wagon  passed  over  it  to  form  ruts  and  de- 
pressions. 


ROAD   RESISTANCES 


15 


To  measure  the  force  applied  to  haul  the  wagon  over  these 
roads  with  varying  grades,  a  simple  modification  of  the  spring 
balance  was  used  with  a  large  index  ringer  moving  over  a  gradu- 
ated arc  to  show  the  pull  in  pounds  and  having  one  end  attached 
to  the  wagon  and  'the  other  to  the  team.  The  record  was  simply 
by  the  eye,  and  showed  that  even  for  the  smoothest  possible 
macadam  the  force  of  traction  was  not  constant,  but  changed 
continually  within  a  limit  of  50  Ibs.  With  dirt  roads  the  force 
varied  from  zero  to  700  Ibs.  in  a  gross  load  of  3,000  Ibs.,  and 
showed  that  it  was  applied  in  a  manner  to  represent  a  succession 


FIG.  4. 


of  rapid  and  violent  jerks.  On  heavy,  smooth  grades  the  force 
was  more  nearly  constant,  as  might  be  expected;  while  to 
start  the  load  under  any  conditions  it  required  about  four  times 
the  force  necessary  to  haul  it. 

From  these  preliminary  observations  the  following  conclusions 
were  drawn :  On  the  smoothest  road  a  team  is  subject  to  a  jerk- 
ing motion  which  greatly  fatigues.  This  is  greatest  on  a  dirt  road 


16  HIGHWAY  ENGINEERING 

because  the  smoother  the  surface  the  less  the  effect  of  such  action. 
It  requires  about  four  times  the  effort  on  a  level  dirt  road  as  upon 
a  level  macadam.  Hard  roads  reduce  the  tractive  force,  and  sand 
roads  increase  the  pull  enormously. 

Supplementing  these  tests,  a  tractograph  was  used  to  deter- 
mine and  record  the  force  applied.  Fig.  4  shows  it  in  position 
on  the  shaft  of  the  wagon.  It  consists  of  an  arm,  placed  longi- 
tudinally along  the  pole,  holding  a  pencil  point  resting  on  a 
stationary  cylinder  covered  with  a  sheet  of  paper.  By  means  of 
the  connections  shown,  the  cylinder  was  made  to  revolve  so  that 
it  completed  1  revolution  in  a  distance  of  1,316  ft.  The  spring 
was  standardized  against  known  weights  varying  by  100  Ibs. 
from  zero  to  1,200,  and  hence  the  compression  of  the  spring  per 
unit  became  known.  From  these  facts  it  was  possible  to  have  a 
sheet  of  paper  divided  into  spaces  corresponding  to  pulls  of  10 
Ibs.,  and  into  other  spaces  corresponding  to  distances  of  100 
ft.,  which  made  known  the  exact  amount  of  pull  and  the  place  at 
which  it  was  applied.  The  compression  of  the  spring  due  to  a 
pull  on  the  double-trees  caused  the  pencil  point  to  move  forward 
on  the  cylinder,  and  thus  make  the  record.  The  diagrams  follow- 
ing show  the  records  obtained:  Fig.  5,  on  an  asphalt  street;  Fig. 
6,  on  a  smooth  macadam  road  in  good  condition ;  Fig.  7,  on  a 
smooth  dirt  road;  and  Fig.  8,  on  a  macadam  road  ascending  a 
hill  of  10  per  cent  grade. 

The  asphalt  was  not  in  good  condition,  being  rough  and  un- 
even, as  is  quite  conclusively  shown  by  the  irregularity  of  the 
record. 

The  macadam  pavement  was  in  excellent  condition. 

The  dirt  road  was  also  in  good  condition;  dry,  firm,  and 
smooth.  It  crossed  the  macadam  pavement  in  two  places, 
and  this  is  shown  by  the  two  high  points  in  the  curve,  being 
due  to  the  fact  that  the  team  stopped  on  either  side  of  the 
pavement. 

Fig.  8  shows  the  effect  of  a  steep  grade  upon  the  tractive 


ROAD   RESISTANCES 


17 


FIG.  5.— Asphalt  Pavement. 


FIG.  6. — Smooth  Macadam  in  Good  Condition. 


18 


HIGHWAY  ENGINEERING 


FIG.  7. — Smooth  Dirt  Road. 


FIG.  8. — Macadam  Road  Ascending  a  10  Per  Cent  Grade. 


ROAD   RESISTANCES 


19 


force,  and  under  the  existing  conditions  the  extremely  irregular 
curve  is  due  to  the  fact  that  the  team  required  continual  urging 
to  ascend  the  hill  at  all.  Compared  to  the  diagram  of  the  level 


TOP  VIEW. 


BOTTOM  VIEW. 
FIG.  9. — Baldwin  Dynograph. 


stretch,  it  indicates  that  about  seven  times  the  force  was  required 
on  the  former  as  upon  the  latter. 

Under  all  conditions,  the  high  points  of  the  curves  at  the  start 


20  HIGHWAY   ENGINEERING 

indicate  that  from  four  to  eight  times  the  effort  to  haul  the  load 
was  required  to  set  it  in  motion. 

If  the  average  amount  of  tractive  force  for  each  road  is  de- 
sired, it  may  be  computed  by  taking  the  area  between  the  zero 
line  and  the  curve  and  dividing  by  the  distance.  From  such 
calculations  it  was  found  that  the  smooth  asphalt  street  required 
26  Ibs.  per  ton,  the  smooth  macadam  road  38  Ibs.  per  ton,  the 
smooth  dirt  road  96  Ibs.  per  ton,  and  on  the  10  per  cent  grade 
136  Ibs.  per  ton. 

A  similar  instrument  for  measuring  the  tractive  force  and  re- 
cording it  automatically  is  the  Baldwin  dynograph,  a  cut  of  which 
is  shown. 

This  instrument  consists  essentially  of  two  flat  springs  with 
ends  connected,  and  centres  separated  from  each  other  by  the 
small  distance  shown.  One  end  of  the  springs  is  attached  to  the 
wagon  and  the  other  end  to  the  team.  Any  force  exerted  by  the 
team  tends  to  draw  the  centres  of  the  springs  together,  and  this 
contraction  is  recorded,  first  by  the  small  pencil  point  moving 
over  the  revolving  cylinder,  which  carries  a  graduated  sheet  of 
paper,  and  second  by  two  index  arms  which  show  against  the 
scale  the  maximum  number  of  pounds  pull,  and  also  an  approxi- 
mate average. 

Grade  Resistance.  Aside  from  the  question  of  drainage,  the 
ideal  road  should  be  as  nearly  level  as  possible,  since  under  these 
conditions  it  favors  the  load  neither  going  or  coming  and  presents 
less  resistance  to  traction. 

To  calculate  what  this  resistance  is,  let  us  assume  in  Fig. 
10  that  G  is  the  centre  of  gravity  of  the  load;  then  GA  is  the 
direction  and  amount  of  the  weight,  while  BG  represents  the  force 
pressing  against  the  inclined  surface  DE.  The  line  EF  represents 
the  rise  per  unit  of  length  DF,  which  is  the  horizontal.  From  the 
two  similar  triangles  we  have  GA  :  AB  :  :  DE  :  EF;  but  GA  is 
the  weight  of  the  load,  DE  is  the  length  of  road,  and  EF  is  the 
rise. 


ROAD   RESISTANCES  21 


Representing  these  by  W,  I,  and  r,  we  have, 
W:AB:  :l:r  or  AB  =  W^ 

but  AB  is  the  resistance  due  to  grade. 
Or  we  may  write  the  formula 


Where  R  =  force  required  to  draw  the  load  on  an  incline, 
F  =  force  required  to  draw  the  load  on  the  level, 
a  =the  grade  expressed  as  a  fraction, 
and      W  =  the  weight  of  the  load  in  pounds. 
Regarding  the  effect  of  grade,  the  Massachusetts  State  High- 
way Commission,  in  its  Report  for  1901,  says  :  "  By  far  the  most 
serious  defect  in  the  old  town  highways  is  the  heavy  grades. 


FIG.  10. 

These  are  not  only  a  tax  on  the  user,  but  they  are  a  constant  and 
burdensome  cost  to  the  municipalities  having  to  care  for  them. 
Taken  as  a  whole,  no  one  improvement  makes  a  better  return  for 
the  money  invested  than  the  cutting  down  of  hills.  Whatever  is 
done  in  this  direction  is  a  permanent  benefit,  as  by  carefully 
grading  a  road  throughout  its  entire  length  between  centres  of 
population  or  business,  the  possible  load  is  increased,  notwith- 
standing no  particular  effort  be  made  to  improve  the  surface." 

The  table  below  shows  the  effect  of  grade  on  the  best  macadam 
roads  in  the  variation  of  the  tractive  force. 


22 


HIGHWAY   ENGINEERING 


Rate  of  Inclination. 

Level 

1  in  500  = 
1  in  100  = 
1  in  80  = 

60  = 


Tractive  Force 
Pounds  per  Ton. 

38 

0.2    of  1  per  cent 42 

1 . 0    per  cent 58 

1 . 25  per  cent 63 


1  in 
1  in 
lin 
1  in 
lin 
1  in 
1  in 
1  in 


1 . 66  per  cent 71 

50=   2.0    per  cent 78 

40=  2 . 5    per  cent 88 

30=  3 . 33  per  cent 104 

25=  4.0    percent 118 

20=   5.0    per  cent 138 

15=   6.66  per  cent 171 

.  238 


10=10.0    percent 


This  is  graphically  represented  in  the  following  cut. 


FIG.  11.— Effect  of  Grade  on  Tractive  Force. 

In  any  case  the  maximum  grade  is  that  which  determines  the 
load  that  may  be  hauled  over  any  section  of  a  road,  and  henc'e  it 
should  always  be  the  object  to  reduce  grade  to  a  minimum. 
Furthermore,  a  horse's  effective  power  for  hauling  rapidly  dimin- 
ishes going  up  inclines,  since  it  is  compelled  to  overcome  the 
increased  resistance  of  gravity  due  to  its  own  weight,  as  well  as 
that  due  to  the  load  itself.  It  should  be  taken  into  consideration, 
however,  that  for  a  short  distance  a  horse  is  able  to  exert  several 
times  its  normal  tractive  pull,  and  it  should  be  remembered  also 
that  the  smoother  and  harder  the  surface  the  poorer  may  be  the 
foothold,  and  consequently  the  less  the  power  that  a  horse  may 
exert. 

This  is  quite  conclusively  demonstrated  by  the  following  table 
taken  from  Baker,  showing  the  effect  of  grade  and  road  covering 


ROAD   RESISTANCES 


23 


upon  the  load  a  horse  may  draw,  the  load  being  in  terms  of  weight 
of  horse: 


Grade 
Per  Cent. 

Iron  Rails. 

Sheet 
Asphalt. 

Broken 
Stone. 

Stone 
Block. 

EARTH  ROAD. 

Best. 

Spongy. 

Muddy. 

'o 

20.00 

10.00 

6.00 

5.00 

3.00 

2.00 

1.00 

1 

6.00 

4.50 

3.33 

2.00 

2.09 

1.50 

0.91 

2 

3.20 

2.67 

2.16 

2.00 

1.51 

1.14 

0.67 

3 

2.00 

1.75 

1.49 

1.40 

1.11 

0.87 

0.54 

4 

1.33 

1.20 

1.05 

1.00 

0.82 

0.66 

0.43 

5 

0.91 

0.83 

0.75 

0.71 

0.60 

0.50 

0.33 

6 

0.62 

0.59 

0.52 

0.50 

0.43 

0.36 

0.25 

7 

0.40 

0.38 

0.34 

0.33 

0.29 

0.25 

0.18 

8 

0.24 

0.22 

0.21 

0.20 

0.18 

0.15 

0.11 

9 

0.15 

0.10 

0.09 

0.09 

0.08 

0.07 

0.05 

10 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

CHAPTER  II 

EARTH   ROADS 

ALMOST  without  exception,  and  naturally  so,  the  highways 
of  the  United  States  have  had  their  beginning  as  dirt  roads. 
Fortunately,  however,  such  preliminary  preparation  or  con- 
struction usually  serves  very  well  as  a  base  upon  which  a  better 
surface  may  be  built,  though  more  frequently  than  not  when 
improvements  are  to  be  begun  it  is  not  only  the  surface  which 
needs  them,  but  the  line,  grade,  and  drainage  as  well. 

The  rectification  of  line  and  grade  necessitate  the  straighten- 
ing of  the  alignment  by  the  elimination  of  curves  and  bends, 
and  of  cutting  down  hills  and  filling  in  valleys,  while  the  im- 
provement in  the  drainage  consists  in  the  application  of  the 
fundamental  principles  governing  the  flow  of  water. 

To-day  most  of  the  roads  of  this  country  are  in  their  original 
condition,  for  dirt  roads  are  the  cheapest  to  construct,  material  is 
always  at  hand,  the  maintenance  afforded  is  apparently  inex- 
pensive, they  require  no  skilled  labor,  and  usually  the  economic 
and  social  conditions  will  not  warrant  a  greater  outlay  for  supe- 
rior ones. 

Those  roads  that  have  been  improved  are  only  a  small  pro- 
portion of  the  whole.  In  the  East,  for  example,  more  than  fifty 
per  cent  of  the  highways  are  absolutely  without  improvement  of 
surfacing,  while  in  the  more  recently  settled  States  of  the  West 
and  Middle  West  this  figure  is  greatly  exceeded.  Thus  in  Illinois, 
over  ninety-seven  per  cent  of  the  roads  are  of  dirt.  These 
facts  would  seem  to  indicate  the  importance  of  properly  building 
and  caring  for  roads  of  such  a  character. 

Earth  roads  are  the  forerunner  of  gravel,  macadam,  and  other 

24 


EARTH   ROADS  25 

improved  pavements,  and  remain  as  they  are  only  so  long  as  they 
successfully  satisfy  the  demands  of  traffic  or  until  it  is  appreci- 
ated that  permanent  good  roads  are  much  less  expensive  to  build 
and  maintain  than  any  other  kind. 

Roads  of  earth  as  usually  constructed  possess  a  great  many 
inherent  qualities  which  unfit  them  for  satisfactory  highways. 
Many  cases  exist  where  the  location  of  the  road  has  been  made 
with  but  little  regard  for  either  grade  or  distance;  but,  aside  from 
these  drawbacks,  often  the  best  has  not  been  made  of  available 
materials  or  existing  conditions. 

Drainage,  perhaps  the  most  important  factor  in  the  main- 
tenance of  a  road,  has  more  often  than  not  been  neglected;  or, 
if  a  realization  of  its  import  has  been  had,  quite  frequently  the 
system  adopted  has  thwarted  the  object  it  was  intended  to  ac- 
complish. 

Considering  three  of  the  more  necessary  requisites — hard- 
ness, smoothness  and  ability  to  shed  water — it  will  be  seen  that 
in  all  three  of  these,  roads  of  dirt  are  lacking,  and  as  a  conse- 
quence, being  easily  broken  up  by  heavy  loads  or  narrow  tires, 
and  always  in  a  condition  to  absorb  moisture  that  may  fall  upon 
them,  they  are  dusty  in  summer  and  muddy  in  wet  weather. 
Both  of  these  conditions  greatly  increase  the  tractive  force,  as 
the  previous  chapter  shows  while  the  presence  of  depressions 
and  irregularities  in  the  surface  permits  water  to  collect, 
only  to  disappear  through  evaporation  or  by  sinking  into  the 
subgrade  which  it  is  one  of  the  functions  of  the  covering  to  pre- 
vent. Furthermore,  because  they  are  so  retentive  of  moisture, 
at  the  breaking  up  of  cold  weather  when  the  frost  is  leaving  the 
ground  earth  roads  are  seriously  affected,  with  the  consequent 
tax  upon  traffic.  If  the  drainage  system  is  properly  planned 
neither  the  muddy  state  after  rain  or  snow  nor  the  broken-up 
condition  so  noticeable  in  spring  resulting  from  the  frost  could 
occur. 

When  a  dirt  road  is  kept  in  good  order,  which  can  only  be 


26  HIGHWAY   ENGINEERING 

secured  through  constant  supervision,  during  the  greater  part  of 
the  year  it  will  serve  quite  satisfactorily  for  the  sort  of  traffic  it  is 
intended  to  carry,  i.e.,  light  traffic,  but  even  so  it  should  be  re- 
membered that  the  tractive  force  expended  on  such  a  road  is 
double  that  required  under  similar  circumstances  on  a  gravel 
pavement  and  four  times  that  on  a  macadam. 

Generally  speaking,  little  technical  skill  is  used  in  the  design 
and  construction  of  dirt  roads,  while  frequently  they  are  formed 
simply  by  a  furrow  being  ploughed  on  each  side  of  the  centre 
line  to  provide  side  ditches,  with  the  material  so  excavated 
thrown  into  the  middle  of  the  roadway  for  the  purpose  of  giving 
crown  and  securing  surface  drainage,  the  traffic  being  supposed 
to  consolidate  it.  This  may  be  supplemented  by  a  road  machine 
to  shape  the  wagon  way  and  side  ditches,  with  grading  and  rolling 
to  follow,  or,  where  the  material  is  stony,  by  pick  and  shovel,  as 
it  is  impossible  to  use  the  machine  with  such  material. 

Sometimes  the  entire  roadway  is  ploughed  and  then  shaped 
with  the  road  scraper  or  road  machine,  but  as  this  leaves  the 
material  soft  and  yielding,  traffic  immediately  produces  ruts  in 
which  water  settles,  making  the  surface  muddy,  and  sinking 
into  the  subgrade. 

The  compacted  soil  wherever  possible  should  remain  undis- 
turbed, either  in  construction  or  repairs  as  it  is  already  hard  and 
firm,  and  will  make  a  better  roadbed  and  absorb  less  moisture 
than  when  it  has  been  loosened.  When,  however,  the  surface  is 
uneven  and  worn,  a  plough  may  often  be  used  to  advantage  to 
take  off  the  irregularities.  The  material  so  removed  should 
be  wasted,  however,  so  that  it  may  not  again  reach  the  road  or 
side  ditches  as  it  has  lost  its  binding  properties.  Fresh  loam, 
free  from  vegetable  matter,  should  be  substituted  in  its  stead  to 
bring  the  road  to  the  proper  cross-section.  Loam  is  by  far  the 
best  material  for  making  such  repairs,  as  it  binds  well,  and  is 
neither  too  retentive  of  moisture,  as  is  clay  on  the  one  hand,  nor 
does  it  permit  water  to  soak  through,  as  does  sand  on  the  other. 


EARTH   ROADS  27 

It  is  needless  to  say  that  such  construction  as  indicated  above 
frequently  fails  of  its  purpose.  For  satisfactory  results  the  wear- 
ing surface  of  a  road  must  be  in  effect  a  roof;  that  is,  the  section 
in  the  middle  must  be  the  highest  part  and  the  travelled  roadway 
should  be  made,  by  consolidation,  as  impervious  to  water  as 
possible,  so  that  the  rain  or  melting  snow  will  flow  freely  and 
quickly  into  the  gutters  alongside. 

Probably  the  best  shape  for  the  cross-section  of  an  earth  road 
is  an  arc  of  a  circle  with  a  gradual  fall  from  the  centre  to  the  sides 
of  about  one  in  twenty,  after  the  surface  has  been  thoroughly 
rolled  or  compacted  by  traffic.  Such  a  surface  can  be  constructed 
and  repaired  with  a  road  machine,  and  a  roller  can  be  used  upon 
it  to  good  advantage.  When  the  surface  is  not  kept  smooth  and 
compact  the  crown  should  be  a  little  steeper  than  1  in  20,  but 
should  normally  never  exceed  1  in  10.  If  the  crown  is  too  great 
the  traffic  will  follow  the  middle  of  the  road,  which  results  in 
ruts  and  ridges  that  retard  the  prompt  shedding  of  the  water  into 
the  side  ditches.  Too  much  crown  is  as  detrimental  as  too  little. 

In  the  construction  of  new  roads,  all  vegetable  matter,  sod, 
roots,  stumps,  rocks,  etc.,  should  first  be  removed  from  the  road- 
way, grading  following  this,  and  rolling  with  sprinkling  for  the  pur- 
pose of  consolidation  finishing  up  the  process.  The  line  should  be 
so  carefully  planned  that  a  maximum  grade  of  about  five  per  cent 
need  never  be  exceeded,  except  in  mountainous  districts  where 
the  topography  is  particularly  difficult  or  rugged.  The  width  of 
wheelway  may  vary  from  twelve  to  forty  feet,  depending  upon 
the  amount  of  traffic  that  is  to  make  use  of  the  thoroughfare. 

Drainage.  Dirt  roads  are,  naturally,  not  ones  where  a  great 
deal  of  money  may  be  or  usually  is  expended,  either  in  their  con- 
struction or  maintenance  and  repair ;  but  it  is  a  fact  that  of  the 
influences  tending  to  make  such  roads  fit  for  traffic  or  absolutely 
impassable,  and  therefore  where  money  may  be  used  to  greatest 
advantage,  drainage  is  by  far  of  most  consequence.  This  is  fre- 
quently referred  to  by  the  remark  that  the  three  most  important 


28  HIGHWAY   ENGINEERING 

factors  in  road  building  and  maintenance  are:  1st,  Drainage; 
2d,  Drainage;  and  3d,  More  Drainage;  and  is  recognized  by  the 
fact  that  even  in  the  most  primitive  roads  ditches  at  the  sides 
are  generally  provided  to  drain  the  subgrade  and  afford  a  water- 
way for  that  which,  falling  on  the  surface,  is  directed  toward 
them  by  the  transverse  slope. 

Drainage  may  be  accomplished  in  three  ways:  1st,  Surface 
drainage;  2d,  Sub-surface  drainage;  and  3d,  Drainage  through 
side  ditches. 

SURFACE  DRAINAGE  has  for  its  object  the  directing  of  any 
water  falling  upon  the  road  covering  toward  the  sides  as  quickly 
as  possible,  so  that  none  may  be  allowed  to  collect  on  the  surface, 
there  to  form  pools,  produce  mud,  and  gradually  sink  through  to 
the  subgrade,  unless  it  be  evaporated  by  sun  and  wind ;  and  it  is 
accomplished  by  crowning  the  road  and  keeping  the  surface  firm, 
hard,  and  smooth,  so  that  the  water  will  easily  and  quickly  run  off. 

By  crowning  is  meant  the  elevation  of  the  centre  of  the  road- 
way above  the  sides:  the  smoother  the  surface  the  less  this 
need  be.  Where  ruts  and  holes  exist,  proper  surface  drainage 
is  impossible,  except  with  excessively  high  crowns.  This  forces 
the  vehicles  to  the  centre,  there  to  produce  more  ruts  and  hollows 
by  tracking,  and  creates  such  steep  shoulders  that  it  becomes  not 
only  difficult,  but  even  dangerous,  for  wagons  to  turn  out  on  them. 

The  transverse  grade  depends  upon  the  longitudinal  slope  of 
the  road  and  the  material  of  which  the  road  is  constructed. 
Consequently,  as  earth  has  a  somewhat  high  friction  factor  com- 
pared with  that  of  other  surfacings,  and  is  easily  cut  up,  it 
will  require  a  much  greater  crown  for  a  dirt  road  than  one  of  a 
smoother  and  harder  nature. 

For  purposes  of  drainage  absolutely  flat  roads,  i.e.,  longitudi- 
nally, are  to  be  discouraged,  though  theoretically  they  are  most 
desirous,  as  all  surface  drainage  would  then  have  to  be  accom- 
plished by  means  of  the  crown  alone.  On  the  other  hand,  the 
longitudinal  grade  should  never  be  so  great  as  to  allow  the  water 


EARTH  ROADS 


29 


to  flow  in  a  torrent  along  the  middle  of  the  roadway  and  wash  out 
gullies;  or,  if  the  grade  is  excessive,  the  transverse  slope  should 
be  proportionally  increased,  within  the  limits  mentioned,  to 
counteract  this  tendency  and  cause  the  water  to  move  diagonally 
across  the  road  toward  the  gutters. 

Where  longitudinal  grade  exists  it  is  customary  to  con- 
struct shoulders,  called  "  thank  you  mams,"  water  breaks,  or 


Incorrect 


False  shoulder 
fand  ditch. 


Correct 


FIG.  12. — This  road  will  be  soft  in  spring  season  and  will  be  only  tem- 
porarily repaired  by  being  worked  in  the  shape  shown  on  left  side  of  drawing. 


FIG.  13. — This  road  will  rut  at  all  points  where  teams  pass  each  other  or 
whenever  they  get  out  near  the  points  A,  A.  C  is  correct  height  above  ditch. 
A,  A  are  too  low  to  hold;  dotted  line  shows  proper  shape. 

breakers,  at  intervals  along  the  road,  to  divert  any  water  flowing 
down  the  centre  to  the  ditches  at  the  sides.  These  breakers  are 
usually  in  the  form  of  a  shoulder  of  earth,  or  stone  or  logs  cov- 
ered with  earth,  set  diagonally  across  the  road,  or  else  shaped  like 
an  obtuse  angle  with  the  apex  in  the  centre  pointing  up-hill. 
Though  necessary,  to  a  degree,  they  increase  the  grade  and  there- 
fore the  tractive  force,  and  on  this  account  are  objectionable; 
but  it  is  also  true  that  on  steep  inclines  they  afford  a  resting- 
place  for  horses  in  the  ascent.  Where  they  join  the  side  ditches 
it  should  not  be  at  too  abrupt  an  angle,  as  they  then  tend  to 
produce  scouring  of  the  gutter  banks,  but  they  must  be  made  to 
approach  them  somewhat  gradually. 


30  HIGHWAY   ENGINEERING 

In  depressions  also,  surface  catch  waters  are  necessary  to 
carry  to  the  side  ditches  that  which  may  have  flowed  down  the 
centre  of  the  road  to  the  low  spot.  These  differ  from  the  others 
in  that  they  are  shallow  trenches  (to  prevent  jolting),  crossing 
the  road  at  right  angles  to  its  axis,  and  having  the  bottom  paved 
with  gravel,  cobble,  or  field  stone. 

When  a  road  exists  on  a  side  hill  it  is  sometimes  suggested 
that  instead  of  the  centre  being  crowned,  the  surface  be  made  to 
slope  toward  the  inner  bank,  so  that  all  the  water  may  flow  in 
the  ditch  there,  instead  of  being  allowed  to  run  over  the  face  of 
the  embankment.  This  is  questionable  practice,  except  on 
sharp  curves,  as  more  water  is  on  the  road,  and  for  a  longer  period 
than  when  the  slope  is  from  the  centre  toward  the  sides.  To 
protect  such  side-hill  roads  from  the  drainage  from  above,  auxili- 
ary ditches  should  be  placed  higher  up  the  hill  to  intercept  water 
flowing  toward  them. 

As  is  easily  recognized,  unless  a  dirt  road  receive  constant 
attention  to  preserve  the  form  of  the  transverse  section,  the 
drainage  must  depend  upon  the  longitudinal  grade  rather  than 
upon  the  transverse  slope,  for  as  the  material  is  soft  the  crown  is 
soon  destroyed  by  traffic.  To  correct  this  tendency,  therefore, 
all  depressions  should  be  immediately  filled  with  good  fresh  earth, 
while  the  surface  should  be  constantly  smoothed  or  rounded  off 
to  the  required  cross-section. 

For  this  purpose  a  harrow  may  be  advantageously  used  when 
the  frost  is  coming  out  of  the  ground  or  when  the  roads  are  thick 
with  mud,  as  it  not  only  evens  off  the  rough  places,  but  cuts  up 
the  road  sufficiently  to  make  it  dry  out  quickly  and  yet  not  im- 
pede the  traffic.  A  railroad  rail  is  used  in  a  similar  way  in  the 
spring  to  drag  over  the  road  for  the  purpose  of  cutting  off  high 
spots  arid  filling  in  low  ones.  This  should  be  from  14  to  16  ft. 
long  and  so  arranged  as  to  lie  diagonally  across  the  roadway  when 
being  hauled  by  a  team.  The  edge  acts  as  the  cutter. 

A  light  scraper,  formed  of  a  piece  of  6  ins.  by  12  ins.  timber, 


EARTH   ROADS 


31 


6  or  7  ft.  long,  and  faced  with  steel  may  be  quite  effectively  used 
in  the  same  way. 

THE  ROAD  DRAG,  forms  of  which  are  shown  in  the  cuts, 
gives  most  excellent  results  also   and  man    miles  of  dirt  road 


FIG.  14.— Railroad  Rail  Drag. 


may  be  kept  in  first-class  repair  by  its  systematic  and  intelligent 
use.  "The  objects  to  be  attained  by  this  method  of  road 
maintenance  are  to  smooth  the  surface  of  the  road  when  it  is  soft 


FIG.  15.— Oak  Plank  Drag. 

and  muddy,  and  at  the  same  time  to  move  a  small  amount  of 
moist  earth  to  the  centre,  thereby  maintaining  the  crown  of  the 
road.  The  drag  is  not  the  implement  to  use  to  move  large  quan- 


32 


HIGHWAY   ENGINEERING 


titles  of  earth,  nor  does  the  maintenance  of  an  earth  road  require 
the  use  of  such  an  implement." 

Rolling,  next  to  drainage,  will  keep  a  dirt  road  in  better  con- 
dition than  anything  else,  though  the  expense  connected  with  it 
may  be  large.  A  heavy  road  roller  will  maintain  a  hard  even 
surface  and  preserve  the  cross-section  intact,  thus  insuring  good 
surface  drainage  and  protecting  the  subgrade  as  well. 

For  this  purpose  one  of  10  to  12  tons  with  a  pressure  of  about 
500  Ibs.  per  lineal  inch  of  roller  wheels  may  be  used  to  excellent 
advantage.  Such  rolling  will  discover  the  weak  spots,  which 


8  or  9  feet- 


FIG.  16.— Split  Log  Drag. 

should  be  immediately  filled  with  new  material  that  binds  readily, 
and  if  employed  in  the  fall  as  the  roads  freeze,  will  keep  them  in 
good  condition  nearly  the  whole  of  the  winter.  In  the  spring 
also,  when  the  frost  is  coming  out  of  the  ground,  it  will  be  found 
that  a  road  roller  may  render  excellent  service  to  keep  the  roads 
in  a  passable  condition. 

Subsurface  Drainage  means  the  draining  of  the  soil,  directly 
beneath  the  covering,  of  that  water  which  may  have  gotten  into 
it  either  by  percolation  from  above  or  from  the  subsoil  below. 
This  is  the  best  method  of  caring  for  a  road,  as  it  drains  the  soil 
of  the  ground  water  and  keeps  it  continually  dry,  precluding 
mud  and  preventing  frost  action.  A  road  built  upon  a  wet  and 


EARTH  ROADS'  35 

undrained  base  will  be  expensive  to  maintain  if  it  is  not  alto- 
gether destroyed  by  the  action  of  water  and  frost.  If  dirt  roads 
satisfied  the  condition  of  having  an  impervious  surface,  no 
water  could  come  from  above,  and  the  underdrains  would  simply 
perform  the  function  of  caring  for  the  ground  water,  but  as  they 
do  not,  some  provision  should  be  made  for  this  condition.  Ground 
water  is,  of  course,  the  very  much  more  important  factor,  and 
particularly  in  excavation,  where  it  tends  to  flow  toward  the  road. 
In  embankment,  on  the  other  hand,  the  water  tends  to  flow 
away  from  the  road. 

It  seldom  happens  that  dirt  roads  need  be  continuously 
underdrained  with  tile  or  some  other  form  of  drain,  for  any  dis- 
tance, but  it  frequently  does  occur  that  at  some  particular  point 
it  is  necessary  to  collect  the  water  in  the  bed  of  the  road,  or  to 
carry  it  from  one  side  to  the  other  by  this  means. 

Under  such  circumstances  the  method  adopted  depends  in  a 
measure  upon  the  nature  of  the  soil.  A  sandy  one  is  easily 
drained,  as  it  does  not  readily  hold  water,  the  crown  and  side 
ditches  being  all  that  are  required  for  the  purpose,  but  with 
clayey  material  the  contrary  is  the  case,  as  it  is  very  retentive  of 
moisture. 

Porous  tile  drains,  made  of  burnt  clay,  seem  to  collect  and 
dispose  of  the  water  most  satisfactorily,  as  they  neither  become 
choked  nor  require  much  grade.  Such  tiles  are  made  in  various 
forms  and  sizes,  but  those  of  circular  cross-section,  five  or  more 
inches  in  diameter,  are  to  be  preferred. 

The  drains  may  be  located  in  a  number  of  ways  along  the 
road,  as,  for  example,  a  single  line  beneath  the  centre  of  the  road- 
bed ;  a  single  line  under  one  of  the  side  ditches ;  two  lines,  one 
beneath  each  of  the  side  ditches ;  or  by  laying  the  drains  herring- 
bone fashion  along  the  middle  of  the  road  with  the  apexes  point- 
ing up-hill,  fifteen  to  thirty  feet  centre  to  centre,  and  the  branches 
falling  away  to  the  side  ditches  into  which  they  discharge  the 
ground  water. 


36 


HIGHWAY   ENGINEERING 


In  any  case  they  should  be  at  a  depth  of  two  or  three  feet  to 
keep  the  subgrade  well  drained  and  prevent  the  pressure  of  heavy 
loads  from  breaking  them. 

To  prevent  small  animals  from  entering  the  drains  and 
choking  them  up,  the  outlets  should  be  protected  with  wire 
netting  placed  over  the  mouth,  and  to  preclude  the  possibility 
of  the  water  eroding  the  banks,  the  ends,  projecting  some  dis- 
tance beyond,  should  be  set  in  some  sort  of  masonry. 

The  method  of  laying  the  tile  with  stone  directly  above  and 
the  earth  on  this  is  shown  in  the  cut.  The  ends  of  each  length 
should  be  in  close  contact  with  the  two  adjoining  ones.  No 
collars  are  necessary,  to  prevent  silt  from  entering  at  the  joints. 

The  size  of  such  drains  depends  on  the  estimated  amount  of 
water  to  be  carried  off,  and  the  grade,  but  should  never  be  smaller 
than  4  or  5  ins.  A  grade  of  1  in  60,  or  1  in.  in  5  ft.,  will  be  found 
sufficient  to  care  for  the  water,  though  as  low  as  J  in.  per  100  ft. 
has  been  used  successfully  in  flat  countries.  Where  the  ground 
is  exceptionally  level,  grade  may  be  secured  by  placing  the  upper 
end  of  the  pipe  line  at  a  less  distance  below  the  surface  than 
the  other  end. 

The  following  table  shows  the  size  of  pipe  required,  with  a 
given  grade,  to  discharge  a  given  quantity  of  water. 


SIZES  OF  DRAIN-PIPE  REQUIRED  FOR  CULVERTS  IN  PROPORTION 
TO  CAPACITY  AND  FALL. 


Inches. 

3-Inch  Fall  per  100  Ft. 
Gallons  per  Minute. 

6-Inch  Fall  per  100  Ft. 
Gallons  per  Minute. 

9-  Inch  Fall  per  100  Ft. 
Gallons  per  Minute. 

6 

129 

183 

224 

8 

265 

375 

460 

9 

355 

503 

617 

10 

463 

655 

803 

12 

730 

1,083 

1,273 

15 

1,282 

1,818 

2,224 

18 

2,022 

2,860 

3,508 

24 

4,152 

5,871 

7,202 

FIG.  18.— Detail  of  Drain. 


EARTH  ROADS  39 

Where  water  is  to  be  carried  beneath  the  roadway  from  one 
side  to  the  other,  clay  or  tile  drains  may  be  used  if  the  quantity 
is  small,  but  where  the  amount  is  large  a  culvert  may  have  to 
be  built. 

A  culvert  is  an  opening  for  the  above  purpose,  constructed  of 
dry  or  wet  masonry,  or  concrete,  with  vertical  sides  and  flat  or 
arched  roof. 

They  should  be  protected  at  the  ends  where  they  emerge 
from  the  embankment  in  the  same  manner  as  are  drains,  only 
to  a  greater  degree,  by  wing  walls  and  an  apron  of  masonry 
to  prevent  erosion,  and  for  this  reason  it  is  better  to  have  a  stone 
foundation  than  one  of  earth. 

Side  Ditches.  For  a  satisfactory  and  cheap  method  of  road 
drainage  there  is  none  better  than  that  afforded  by  the  side 
ditches,  and  most  frequently  this  is  the  only  effective  one  em- 
ployed to  any  extent,  or  the  only  one  found  necessary.  These 
ditches  are  placed  on  both  sides  of  the  roadway  wherever  pos- 
sible, not  only  to  carry  off  the  water  falling  on  the  surface  and 
draining  into  them,  but  also  to  intercept  that  which  may  flow 
from  neighboring  land  toward  the  highway,  and,  furthermore, 
perform  the  function,  when  deep  enough,  of  draining  the  sub- 
grade  and  keeping  it  continually  dry. 

Where  open  ditches  may  not  be  conveniently  used  at  the 
sides,  others,  as  shown  by  the  cuts,  are  employed  to  perform  a 
similar  function. 

All  ditches  should  be  of  such  a  cross-section  that  a  scraper  or 
road  machine  may  be  easily  used  in  their  formation  and  main- 
tenance, as  when  so  constructed  they  are  easier  and  cheaper  to 
keep  in  repair.  The  following  figures  show  the  sections  of  a 
shallow  and  of  a  deep  side  ditch  where  this  condition  obtains. 
The  shallow  ditch  is,  all  things  considered,  much  the  more  pref- 
erable, not  only  because,  from  the  standpoint  of  cost  of  con- 
struction and  maintenance  and  repair,  it  is  cheaper,  but  it  also 
affords  an  easy  and  safe  place  to  turn  out  when  teams  are  crowded 


40  HIGHWAY   ENGINEERING 

to  the  side;  it  should  be  remembered,  on  the  other  hand,  how- 
ever, that  the  deeper  a  ditch  is  the  better  the  subgrade  will  be 
drained.  Side  ditches  should  be  kept  as  free  as  possible  from  for- 
eign matter,  such  as  brush,  sticks,  stones,  weeds,  etc.,  since  its 
presence  prevents  the  speedy  discharge  of  the  water  gathered 
there.  This  latter  can  only  be  secured  by  a  grade  sufficient  to 
carry  off  the  water  and  any  suspended  matter  it  may  contain, 
yet  not  so  great  as  to  cause  the  washing  away  of  the  side  banks. 

It  is  needless  to  say  that  side  ditches  should  never  so  far  fail 
in  their  function  as  to  permit  water  to  stand  in  them  for  any 
length  of  time,  for  this  simply  keeps  the  subgrade  soft  and  moist, 
and  it  should  be  rectified  by  either  a  change  of  grade  or  the 
cleaning  out  of  the  ditch  and  its  outlet.  The  transporting  power 
of  water  is  quite  considerable,  velocities  of  thirty  feet  per  min- 
ute being  able  to  move  fine  clay,  while  double  that  velocity 
or  sixty  feet  per  minute  will  move  gravel. 

On  steep  grades  it  is  well  to  have  the  ditches  so  far  removed 
from  the  road  that  a  strip  of  brush  or  small  trees  may  be  grown 
between  them  to  afford  protection  to  the  side  slope  next  the  road, 
by  the  roots,  and  thus  prevent  the  scouring  action  of  the  water 
with  the  ultimate  destruction  of  the  road.  Much  more  fre- 
quently, however,  the  same  effect  is  accomplished  by  sodding 
the  side  slopes  or  laying  field  stone  in  the  gutters.  Slopes  of  1  in 
150  to  1  in  125  give  very  satisfactory  results  for  this  sort  of  drain- 
age, but  often  these  values  must  necessarily  be  greatly  exceeded 
because  of  the  grade  in  the  road  itself.  Where  such  is  the  case, 
the  erosion  in  the  ditch  may  then  be  quite  considerable  unless 
some  provision  as  noted  above  is  made  to  counteract  it.  The 
tendency  under  these  circumstances  will  be  for  the  water  to  cut 
away  the  material  on  the  longitudinal  section  midway  be- 
tween the  bottom  and  the  top  of  the  hill,  with  the  result 
that  the  grade  is  greatly  increased  at  a  point  where,  if  any- 
thing, it  should  be  diminished,  i.e.,  at  the  top  of  the  hill,  for 
it  is  here  that  the  horse  is  most  fatigued,  and  where,  if  a  change 


EARTH   ROADS 


41 


is  to  be  made  at  all,  it  should  be  toward  diminishing  the  tractive 
force  rather  than  increasing  it  so  that  the  least  effort  will  be  re- 
quired. 

Crown.  The  transverse  contour  may  be  in  the  form  of  a 
gentle  curve  with  the  highest  point  at  the  centre,  or  of  two  planes 
intersecting  at  the  middle  of  the  road.  Where  the  curve  is  used, 
either  circular  or  parabolic  may  be  taken,  but  in  dirt  roads  this 
makes  little  difference  as  such  small  discrepancies  are  impossible 
to  preserve  in  so  soft  a  material. 

The  following  figures  19,  20  and  21,  show  the  variation  in 
crown  for  different  materials. 


-Width-between-diteb.es- 

— Width-of-driveway — 

Crown  l"to  1  foot 


FIG.  19.— Gravelly  Loam  or  Ordinary  Soil. 


FIG.  20.— Sandy  Loam. 


For  clay  roada  deep 

wand  wide  ditches  are 

absolutely 


FIG.  21. — Clay  Road. 


With  smooth,  hard  pavements,  where  the  friction  is  small  and 
which  do  not  yield  to  the  action  of  traffic,  the  inclination  may  be 
made  correspondingly  small;  but  in  dirt  roads,  where  both  of 
these  conditions  are  quickly  destroyed,  the  maximum  must  be 


42  HIGHWAY   ENGINEERING 

applied;  crown,  however,  should  be  given  in  moderation,  for  too 
much  of  it  concentrates  the  traffic  in  the  centre,  causing  ruts 
which  hold  water,  and  hence  the  surface  is  not  so  dry  as  with  a 
flatter  contour. 

For  satisfactory  surface  drainage  and  yet  not  too  excessive 
crown,  a  rise  of  T1Tr,  the  half  width  of  wheelway,  is  recommended 
for  dirt  roads.  Frequently  the  following  rule  is  given  for 
crowning  country  roads — at  J  the  distance  from  the  centre  give 
J-  of  the  total  rise,  and  at  J  the  distance  f  of  the  total  rise. 

Width.  The  right  of  way,  which  means  the  space  between 
fence  lines,  varies  in  the  United  States  from  40  to  100  feet.  In 
dirt  roads  it  is  always  well  to  appropriate  as  much  of  this  as  is 


FIG.  22.— Too  Wide  for  the  Traffic.     Dotted  Line  Shows  Proper  Shape. 

consistent  for  the  wheelway,  not  only  to  prevent  the  effect  of 
traffic  following  the  same  line,  but  to  derive  also  the  ad- 
vantage of  the  effects  of  sun  and  wind  which,  next  to  drain- 
age, are  the  most  important  factors  in  keeping  the  roadway  in  a 
dry  condition.  Particularly  in  wet  weather  are  wide  roads  ad- 
vantageous, as  they  permit  a  choice  of  route.  On  the  other  hand, 
while  every  road  should  be  wide  enough  to  accommodate  the 
traffic  it  is  intended  to  carry,  it  should  be  noted  that  any  increase 
in  the  width  means  an  increase  in  the  cost  of  construction  and  in 
the  item  of  maintenance  and  repair. 

Very  frequently  in  small  towns  where  dirt  roads  are  exten- 
sively used  the  width  of  wheelway,  forty  to  forty-five  feet,  is  far 
greater  than  the  demands  of  the  traffic  require  or  is  desirable  from 
an  economical  standpoint.  A  much  better  arrangement  is  a 
narrower  wheelway  with  the  rest  of  the  space  devoted  to  grass 
plots,  whereby  the  cost  of  repairs  is  reduced  and  the  appearance 
of  the  street  improved. 


EARTH   ROADS  43 

On  purely  rural  highways,  where  the  traffic  is  light,  the  width 
of  travelled  way  will  be  about  eight  feet  as  a  minimum,  but  these 
are  always  provided  with  shoulders  that  make  it  possible  for  the 
teams  to  turn  out  in  passing  each  other. 

Side  Slopes.  The  slope  of  the  banks  to  both  the  ditches  and 
the  sides  of  the  roadbed,  either  in  excavation  or  in  embankment, 
depends  primarily  upon  the  nature  of  the  material.  Where  this 
is  firm  and  will  stand,  as  small  a  slope  as  that  represented  by  a 
vertical  rise  of  4  ft.  in  1  ft.  horizontal  may  be  sufficient;  but 
where  it  is  soft  or  yielding,  a  slope  of  1  ft.  vertical  to  4  ft.  horizon- 
tal may  be  required.  In  the  latter  case  the  longitudinal  grade  al- 
so will  have  to  be  small  to  prevent  the  transportation  of  material, 
unless  some  method  of  protecting  the  ditches  is  adopted. 

The  most  common  slope  is  1  on  1J,  or  a  rise  of  1  ft.  in  a  dis- 
tance of  1J  ft.,  since  at  that  angle  most  earth  embankment  will 
stand.  The  following  values  are  those  most  generally  used 
with  other  materials. 

H.       V. 

Loose  earth,  loam,  and  gravel 1£  to  1 

Sand 2    to  1 

Soft  greasy  clay 3    to  1 

Rock i  to  1 

It  is  always  better  to  have  the  side  slopes  as  gentle  as  possible, 
as  the  broader  the  ditch  the  less  likelihood  there  is  of  the  material 
slipping  when  water-soaked,  in  which  condition  it  is  least  stable. 

The  term  earthwork  is  applied  to  all  operations  of  embank- 
ment or  excavation,  which  include  rock  or  earth,  in  the  prepara- 
tion of  the  roadbed.  The  excavation  should  always  be  in  such 
amount,  within  economic  limits  of  haul,  as  to  equal  the  embank- 
ment, for,  where  this  does  not  obtain,  material  in  the  one  case 
must  be  borrowed  from  off  the  right  of  way  to  satisfy  the  "  fill," 
while  in  the  other  it  becomes  necessary  to  waste  the  excess  of 
"cut."  In  the  former  case  the  material  is  taken  from  a  borrow 
pit,  while  in  the  latter  the  place  where  it  is  wasted  is  called  a 
spoil  bank.  In  balancing  "  cut "  and  "  fill "  it  is  very  necessary  to 


44  HIGHWAY   ENGINEERING 

remember  that  different  materials  occupy  greater  or  less  space 
after  excavation  than  before ;  thus  the  amount  of  shrinkage  after 
displacement  is  shown  by  the  figures  below. 

Gravel 8  per  cent 

Gravel  and  sand 9  per  cent 

Clay  and  clay  earths 10  per  cent 

Loam  and  light  sandy  earths 12  per  cent 

Loose  vegetable  soil 15  per  cent 

Puddled  clay 25  per  cent 

On  the  other  hand,  rock  increases  in  bulk  by  about  fifty 
per  cent.  As  an  example,  and  to  show  the  importance  of  con- 
sidering this  change,  we  may  quote  from  the  Massachusetts 
Highway  Commission's  Report.  Owing  to  the  depth  of  fill  in  an 
embankment  and  the  character  of  the  ground,  it  was  deemed  in- 
advisable to  place  the  surfacing  of  broken  stone,  curbings,  paved 
gutters,  etc.,  until  a  year  had  elapsed,  "to  give  the  embankment 
time  to  settle,  thus  saving  the  loss  of  costly  material  and  the  ex- 
pense of  repairs." 

Maintenance  and  Repair.  A  typical  country  road  is  usually 
maintained  and  kept  in  repair  by  the  aid  of  labor  which  is 
ignorant  of  the  fundamental  principles  underlying  such  work, 
or  careless  of  the  results.  Furthermore,  the  undertaking  is 
indulged  in  perhaps  once  or  twice  a  year,  and  the  havoc  created 
then  is  supposed  to  keep  the  road  in  good  condition  the  rest  of  the 
time.  This  method  is  absolutely  at  variance  with  the  needs,  for 
a  dirt  road  is  one  that  is  readily  broken  up,  and  it  is  only  by  con- 
stant and  careful  attention  that  it  may  be  preserved  in  a  highly 
satisfactory  state.  Under  all  circumstances,  for  good  results,  the 
system  of  continuous  repairs,  as  adopted  by  one  of  the  New  Eng- 
land States,  should  be  employed.  This  approaches  more  or  less 
closely  that  employed  in  France,  where  a  laborer  is  put  in  charge 
of  a  piece  of  road  adjacent  to  his  dwelling,  and  for  which  he  is  en- 
tirely responsible.  Applied  to  dirt  roads,  it  would  mean  the  daily 
or  periodic  inspection  of  the  section  in  question,  the  removal  of 


EARTH  ROADS  45 

all  stones,  etc.,  from  the  highway,  the  filling  up  of  ruts,  depres- 
sions, and  holes,  the  careful  attention  to  the  surface,  crown,  etc., 
the  removal  of  brush,  weeds,  sod,  sticks,  and  stones  from  side 
ditches,  the  cleaning  out  of  the  same,  and  of  all  drains  or  culverts 
to  permit  the  free  flow  of  water,  together  with  the  removal  of 
snow  in  winter,  and  perhaps  the  application  of  oil  in  summer  to 
prevent  dust. 

One  of  the  worst  features  in  present-day  practice  of  road 
maintenance  is  that  through  ignorance,  instead  of  removing  a 
thin  surface  layer  of  material  that  is  valueless  as  a  road  metal, 
having  lost  all  its  binding  properties,  there  is  added  to  this  more 
of  the  same  character  from  the  side  ditches.  The  consequence 
is  that  this  is  soon  reconverted  into  dust  or  mud  and  quickly 
deposited  again  in  the  side  ditches  from  which  it  came,  with  the 
loss  of  the  crown  and  the  filling  up  of  the  ditch  as  the  resultant 
twofold  disadvantage.  Any  material  that  is  lacking  in  binding 
power  should  be  removed  from  the  roadway  to  such  a  distance 
that  there  is  no  possibility  of  its  getting  back  there  again. 


CHAPTER   III 

GRAVEL   ROADS 

GRAVEL  roads  seem  to  occupy  an  intermediate  place  between 
those  of  earth  and  broken  stone,  in  the  tractive  force  required, 
character  of  surfacing,  and  cost  of  construction. 

On  a  well-made  gravel  road  a  horse  is  able  to  pull  just  twice 
the  load  he  is  capable  of  hauling  on  a  dirt  road,  while  this  is  only 
about  one-half  of  what  may  be  drawn  on  a  macadam  pavement. 
Gravel  well  applied  makes  a  surface  far  superior  to  dirt,  yet  not 
possessing  the  wearing  qualities  of  broken  stone,  and  for  this 
reason  such  roads  are  most  frequently  built  under  conditions 
where  a  covering  other  than  earth  is  required,  where  the  loads  and 
traffic  are  light,  and  where  the  cost  of  broken  stone  is  prohibitive. 
That  is  to  say,  gravel  roads  are  best  suited  to  country  highways 
and  park  drives. 

When  stone  roads  are  either  impossible  or  impracticable, 
either  because  of  the  lack  of  suitable  material  in  the  vicinity, 
the  excessive  cost  of  the  stone,  or  because  of  some  other  reason, 
gravel,  if  properly  laid,  will  make  a  very  superior  substitute. 

The  gravel  selected  for  road-building  purposes  will  generally 
be  that  most  conveniently  located,  thereby  introducing  the 
possibility  of  great  variety,  for  with  long  hauls,  i.e.,  in  excess  of 
a  mile  and  one-half,  the  item  of  transportation  so  increases  the 
cost  of  construction  as  to  make  broken  stone  desirable. 

Gravel  consists  of  an  aggregation  of  small  stones,  more  or  less 
worn  and  rounded  by  glacial  or  water  action,  and  varying  in  size 
from  that  of  a  pea  to  pebbles  two  or  more  inches  in  diameter,  and 
usually  associated  with  some  other  and  finer  material  that  acts 
as  a  binder  to  hold  the  stones  together.  To  be  a  serviceable  and 

46 


GRAVEL   ROADS  47 

satisfactory  road  metal,  it  should  possess  the  following  character- 
istics. 

The  pebbles  themselves  must  be  hard  to  resist  the  abrasive 
action  of  horses'  hoofs  and  wagon  wheels,  and  tough  to  with- 
stand the  blows  of  the  horses'  feet.  The  tougher  and  harder  the 
stones,  therefore,  the  longer  will  they  resist  this  action.  Besides 
possessing  these  qualities,  however,  the  pebbles  should  be  sharp 
and  angular,  since  with  sides  worn  smooth  they  freely  move  one 
upon  the  other  and  thus  lack  the  characteristic  mechanical  bond 
possessed  by  broken  stone. 

Between  pebbles  and  binder  there  should  be  such  a  relation 
that  all  the  voids  in  the  stones  are  completely  filled,  and  in  a 
manner  to  give  the  maximum  cementing  effect.  If  this  disposi- 
tion of  material  or  ratio  is  exceeded,  the  binder  must  necessarily 
take  some  of  the  wear,  a  function  which  it  is  not  supposed  to 
perform  and  to  which  it  is  absolutely  unsuited,  while  if  not 
maintained,  the  bond  will  be  weak  and  fail  to  hold  the  stones 
together. 

Finally,  the  binder  itself  must  possess  to  a  marked  degree  the 
property  of  cementing  the  stones  together,  as  otherwise  the 
smooth  pebbles  move  under  traffic,  similar  to  a  mass  of  loose 
stone,  and  there  is  little  stability  in  the  pavement. 

The  binder  may  consist  of  loam,  clay,  iron  oxide,  silica,  lime- 
stone, or  one  of  a  number  of  other  materials,  but  that  most  gen- 
erally found  mixed  with  the  stone  is  clay.  Where  the  climatic 
conditions  are  favorable,  this  forms  a  very  satisfactory  bond,  but 
with  excessive  rains  or  continued  dry  spells  the  cementing  prop- 
erties are  quickly  lost.  In  hot,  dry  weather  the  lack  of  moisture 
and  the  heat  cause  the  clay  to  crack,  leaving  the  pebbles  as  so 
many  loose  stones  on  the  surface,  while  in  wet  weather  the  rain 
turns  the  clay  to  mud  in  which  the  stones  soon  disappear  under 
the  pressure  of  the  wheels. 

"  Probably  the  best  loam  binder  is  one  in  which  the  clayey 
cement  is  very  tenacious,  and  in  such  quantity  that  the  gravel 


48  HIGHWAY   ENGINEERING 

will  stick  to  the  shovel  enough  to  bother  the  workmen  in  handling 
it."  If  such  a  gravel  possesses  from  three  to  ten  per  cent  of 
chert  *  as  well,  the  binding  power  will  be  further  augmented,  as 
the  latter  is  easily  crushed  and  possesses  superior  cementing 
qualities. 

The  mechanical  bond  spoken  of  above  as  existing  in  material 
composed  of  angular  fragments,  is  an  important  factor  in  the  con- 
solidation of  either  gravel  or  broken-stone  roads,  the  reason  being 
that  the  irregularities  and  corners  adjust  themselves  to  each  other 
in  such  a  manner  as  to  become  wedged  or  locked  together.  For 
a  somewhat  similar  result,  in  using  gravel,  the  size  should  vary 
between  about  \  in.  and  3  ins.  so  that  the  smaller  particles  may 
fit  into  the  interstices  formed  by  the  larger.  Material  smaller 
than  \  in.  is  too  easily  crushed  in  the  pavement  to  be  of  much 
service,  and  larger  than  3  ins.  tends  to  make  the  road  rough. 

Gravel  will  be  found  to  vary  quite  considerably,  both  in 
regard  to  the  character  of  the  stone  and  the  quality  and  quantity 
of  the  binder  present.  River  and  seaside  gravel  are  hardly  ever 
so  good  as  that  from  pits  because  the  smoothness  of  the  stones 
permits  them  to  turn  under  pressure  even  when  associated  with  a 
good  binder.  Pit  or  bank  gravel  generally  contains  more  cement- 
ing material  than  other  kinds,  and  the  stones  are  less  apt  to  be 
water- worn.  The  poorer  kinds  are,  however,  sometimes  used  as  a 
foundation,  or  mixed  with  more  binder  to  secure  better  results. 

A  good  gravel  may  be  determined  by  an  inspection  of  it  in  the 
pit.  If  it  stands  with  a  vertical  face,  is  compact,  free  from 
strata  of  sand,  hard,  needs  a  pick  to  dislodge  it,  and  breaks  in 
chunks,  it  will  make  an  excellent  road  surfacing  and  require  no 
further  treatment. 

That  containing  a  ferruginous  clay,  together  with  sharp 
angular  stones,  is  exceptionally  good,  as  exposure  to  the  air 
hardens  the  binder  and  produces  the  more  complete  consolida- 
tion of  the  material. 

*  "  Chert  is  a  silicious  rock,  a  variety  of  quartz,  somewhat  like  flint." 


GRAVEL  ROADS  49 

Usually  the  gravels  occur  in  beds  containing  pebbles  fairly 
uniform  in  size  so  that  no  screening  is  necessary,  but  where  such 
condition  does  not  obtain,  a  recourse  must  be  had  to  it  to  remove 
the  larger  stones  or  the  excess  of  earthy  material.  In  the  latter 
case,  two  screens  are  employed,  one  passing  material  under  2f  ins. 
in  diameter  and  the  other  of  f  in.  diameter.  That  which  passes 
the  smaller  sieve  may  be  appropriately  used  for  side  paths,  while 
that  retained  on  the  larger  screen  may  be  used  as  a  foundation 
or  crushed  to  smaller  sizes. 

Screening,  however,  seems  to  possess  a  marked  tendency  to 
remove  more  of  the  binder  than  is  desirable,  and  should  be  re- 
sorted to  only  when  absolutely  necessary. 

In  the  state-aid  roads  of  Massachusetts  where  screening  has 
been  employed,  the  material  is  sized  into  J  in.,  If  in.,  and  2f  in. 
stone.  These  are  spread  in  courses,  the  larger  on  the  bottom ; 
each  layer  being  separately  sprinkled  and  rolled  as  in  the  con- 
struction of  stone  roads.  Pebbles  failing  to  pass  the  largest 
screen  are  sent  to  the  crusher  and  again  sized  with  the  other  gravel. 

Drainage.  The  complete  and  satisfactory  drainage  of  a 
gravel  road  is  very  essential  and  perhaps  more  important  than 
with  any  other  class  as  the  material,  particularly  the  binder,  is  so 
easily  displaced  by  water  flowing  over  the  road. 

The  purpose  of  the  covering  should  be  to  form  a  smooth,  hard, 
impervious  surface,  and  so  distribute  the  load  that  the  founda- 
tion may  be  able  to  resist  the  pressure  without  failure  and  con- 
sequent rutting  of  the  surface. 

If  water  is  allowed  to  remain  in  the  ruts  and  hollows,  the  sub- 
grade  soon  becomes  softened,  the  binder  loses  its  properties,  the 
pebbles  become  loosened,  and  the  wheels  cut  through  to  the  sub- 
grade.  The  drier  the  subsoil  the  firmer  it  will  be  and  the  better 
able  to  perform  its  function  as  a  foundation.  In  fact,  gravel  on  a 
soft  wet  base  is  practically  useless,  as  it  is  readily  forced  into  the 
mud  below.  Because  a  gravel  road  is  less  pervious,  and  sheds 
more  water  than  one  of  dirt,  the  side  ditches  or  drains  should  be 

4 


50  HIGHWAY   ENGINEERING 

both  wide  and  deep :  deep  so  that  they  may  drain  the  subgrade 
of  the  roadbed  well,  and  wide  so  that  they  may  successfully  care 
for  the  water  diverted  toward  them.  On  steep  grades  the 
ditches  are  paved  with  cobble  to  prevent  erosion,  while  on  city 
streets  the  gutters  next  the  curbs  are  similarly  constructed  to 
protect  the  sides  from  wagon  wheels.  In  the  latter  case  the 
stones  serve  the  purpose  of  a  shoulder  for  the  gravel  and  prevent 
it  from  spreading. 

The  longitudinal  grade,  from  the  standpoint  of  drainage, 
should  be  as  small  as  possible,  as  gullies  are  quickly  formed  by 
the  water  flowing  along  the  axis  of  the  road  and  the  binder  and 
pebbles  are  washed  away.  In  such  cases,  the  crown  is  made  cor- 
respondingly high,  to  get  the  water  off  the  roadway  and  into  the 
side  ditches  as  soon  as  possible. 

Under  normal  conditions  the  crown  need  not  be  so  great  as 
that  employed  in  earth  roads,  for  the  water  encounters  less 
resistance  on  the  smooth  surface  of  the  gravel  and  reaches  the 
ditches  with  a  much  smaller  grade.  A  crown  of  J  to  J  in.  per 
foot  of  width  or  a  rise  at  centre  of  -£$  the  half  width  of  wheel- 
way  is  quite  satisfactory. 

The  crown,  however,  depends  very  largely  on  the  traffic, 
grade,  and  method  of  repairs,  and  for  each  set  of  conditions 
should  be  modified  to  suit.  For  example,  on  highways  where 
the  traffic  is  excessive  the  crown  is  proportionally  increased; 
first,  because  the  greater  the  haulage  the  greater  the  amount  of 
wear  to  the  surface  between  periods  of  repair,  and  second, 
because  ruts  are  more  quickly  made,  retarding  the  flow  of  water 
which  the  crown  must  counteract. 

Construction.  There  are  two  general  methods  of  building 
gravel  roads,  known  as  Surface  Construction,  and  Trench  Con- 
struction. 

SURFACE  CONSTRUCTION  is  perhaps  very  much  less  satis- 
factory than  the  other  because  it  exercises  less  care  in  the  work. 
In  its  crudest  form  it  simply  means  that  upon  the  old  and  un- 


GRAVEL   ROADS  51 

prepared  roadbed  a  certain  amount  of  gravel  is  dumped  or  strewn 
with  the  hope  that  traffic  will  consolidate  it  into  an  impervious 
pavement.  This  may  be  the  case  with  very  exceptional  con- 
ditions, i.e.,  where  the  roadbed  is  dry,  hard,  and  well  drained, 
and  where  the  gravel  is  of  such  character  that  it  binds  well  and 
quickly  under  the  action  of  wagon  wheels  and  horses'  hoofs; 
but  it  is  generally  bad  practice  and  only  a  makeshift  at  best.  It 
is  true  that  the  Massachusetts  Highway  Commission  has  found 
gravel  roads  thus  built  in  excellent  repair  after  twelve  years  of 
service,  but  these  are  isolated  cases  and  where  the  factors  have 
been  carefully  studied  and  found  extremely  favorable. 

On  the  contrary,  the  more  care  and  preparation  the  original 
dirt  road  receives  for  the  reception  of  the  gravel  covering,  the 
better  will  it  serve  its  purpose  and  the  less  it  will  cost  to  maintain 
and  repair.  The  roadway,  therefore,  should  first  be  properly 
graded,  crowned,  and  rolled  to  secure  a  firm,  even  surface,  and 
the  drainage  carefully  inspected,  both  as  to  the  side  ditches  and 
subsurface  drains,  to  see  that  the  water  is  capable  of  being  car- 
ried away  as  soon  as  possible.  With  such  assurance,  the  gravel 
may  be  placed  upon  this  as  a  foundation,  being  distributed  over 
the  surface  in  successive  layers  three  to  six  inches  deep.  Each 
course  is  liberally  sprinkled  with  water  to  insure  speedy  consolida- 
tion, and  a  road  roller  of  ten  tons  is  then  used  to  perfect  this. 
Should  depressions  develop  during  the  rolling,  more  material 
must  be  spread  upon  such  places,  until,  after  a  continuance  of  the 
process,  the  entire  surface  has  been  brought  to  the  proper  grade. 
If  the  consolidation  is  satisfactory,  a  second  layer  may  be  applied 
and  treated  in  the  same  manner,  the  operation  being  repeated 
until  the  pavement  is  of  the  required  thickness. 

In  some  cases  the  traffic  alone  is  allowed  to  perform  the  func- 
tion of  consolidating  each  course  of  material,  but  it  is  not  nearly 
so  satisfactory,  as  it  introduces  foreign  matter  between  the 
different  layers,  thus  precluding  as  firm  a  bond,  and  requires 
very  much  more  time  to  accomplish.  Unless  the  subgrade  is 


52  HIGHWAY   ENGINEERING 

drained  properly  and  prepared  to  receive  the  gravel,  frost  and 
rain  easily  affect  the  foundation  so  that  a  considerable  number  of 
months  may  elapse  before  the  road  is  in  any  other  than  a  very 
unsatisfactory  condition. 

The  most  critical  period  in  the  life  of  a  gravel  road  is  when 
traffic  is  first  admitted  to  it,  as  then  ruts  are  quickly  and  easily 
formed  to  remain  as  permanent  defects  unless  rectified  at  once. 

Massachusetts  has  adopted  the  following  method  in  the  con- 
struction of  gravel  roads.  The  bed  is  examined  for  low,  wet, 
and  weak  spots,  and  carefully  prepared  as  a  foundation,  by 
removing  objectionable  material,  laying  drains,  digging  ditches, 
and  thorough  rolling,  to  receive  the  gravel  to  be  placed  upon  it. 
This  consists  of  a  bottom  course  of  screenings  of  the  required 
depth,  with  a  surfacing  coat  of  one-inch  gravel  mixed  with  con- 
siderable binder  above  it.  The  whole  road  is  then  rolled  until  it 
becomes  hard  and  smooth,  being  well  watered  during  the  opera- 
tion to  assist  consolidation. 

TRENCH  CONSTRUCTION  varies  but  little  from  the  other  form 
except  in  the  fact  that  a  trench  is  excavated  of  the  required 
width  and  from  eight  to  ten  inches  deep,  for  the  purpose  of  hold- 
ing the  gravel  in  place  by  means  of  the  shoulders  at  the  sides. 
The  bottom  of  the  trench  or  foundation  for  the  gravel,  prepared 
as  in  the  previous  case,  may  be  flat  or  correspond  in  section  to 
that  of  the  surface  of  the  road,  the  latter  requiring  less  material. 

The  advantage  of  this  over  the  other  method  is  in  the  fact  that 
the  shoulders  hold  the  gravel  in  place  and  prevent  its  thinning 
out  at  the  centre  by  working  over  to  the  sides.  The  material 
is  applied  as  in  surface  construction. 

In  either  form  of  construction,  it  is  better  that  the  gravel 
vary  uniformly  between  J  in.  and  3  ins.  so  that  the  voids  be- 
tween the  larger  pebbles  may  be  filled  by  the  smaller  ones.  If 
this  is  not  the  case,  screening  should  be  resorted  to,  so  that 
material  over  2J  or  3  ins.  and  less  than  %  in.  may  be  rejected. 
The  larger  size  may  be  used  as  a  foundation  upon  which  the 


GRAVEL   ROADS  53 

other  is  placed,  and  when  so  used  should  be  rolled  and  consoli- 
dated to  a  depth  of  about  4  ins.,  before  the  smaller  size  is  ap- 
plied. This  is  put  in  layers,  each  being  thoroughly  sprinkled 
and  rolled,  while  the  top  layer  is  mixed  with  an  excess  of  binder. 

Experience  in  Massachusetts  has  shown  that  where  the 
gravel  is  screened  excellent  results  are  obtained,  and  that  while 
the  roads  wear  more  quickly  than  macadam,  due  to  ravelling,  this 
is  not  serious.  Such  roads  are  more  easily  maintained  than  others. 

GRAVEL  ON  EARTH  ROAD.  Frequently  the  application  of  a 
three-  or  four-inch  layer  of  gravel  to  an  earth  road  will  greatly 
improve  the  surface.  It  should  be  remembered,  however,  that 
this  will  not  be  the  case  if  the  soil  is  wet,  and  if  such  conditions 
prevail  the  subsoil  must  in  some  way  be  underdrained.  If  the 
material  is  clay  instead  of  loam,  gravel  to  a  depth  of  six  inches 
will  be  necessary.  Under  any  circumstances  the  gravel  should  be 
thick  enough  to  prevent  the  traffic  from  forcing  it  into  the  clay 
below  and  at  the  same  time  prevent  the  surface  water  from 
percolating  to  the  soil  beneath,  saturating  it  and  weakening  it. 

It  is  needless  to  dump  the  gravel  into  ruts,  mud-holes,  etc., 
and  look  for  traffic  to  consolidate  this  and  produce  a  superior 
highway.  Drainage  must  be  attended  to  first,  last,  and  all  the 
time,  or  the  results  will  be  anything  but  satisfactory. 

Maintenance  and  Repairs.  MAINTENANCE.  "1.  After  a 
newly  constructed  gravel  road  has  been  thrown  open  to  traffic, 
it  should  be  carefully  watched  in  order  that  any  defects  may  be 
remedied  at  once.  Shallow  ruts  and  depressions  should  be  re- 
paired without  delay,  or  serious  damage  will  be  the  result.  In 
repairing  a  new  road  the  gravel  on  the  sides  of  the  depression 
may  be  raked  back  in  place ;  but  after  a  time  it  will  become  neces- 
sary to  fill  the  depressions  with  new  material.  In  the  latter 
case  the  old  hardened  surface  should  be  slightly  loosened  with 
rakes  in  order  to  get  a  bond  between  the  old  and  the  new  material. 
The  gravel  used  should  be  smaller  in  size  and  should  also  contain 
more  binding  material  than  that  used  in  the  construction.  This 


54  HIGHWAY  ENGINEERING 

material  should  be  stored  in  piles  along  the  road-side,  containing 
fifteen  to  twenty  cubic  yards  each.  Smaller  piles  are  soon  scat- 
tered and  wasted.  2.  Loose  stones  should  be  raked  off  the  road 
surface  as  soon  as  they  appear.  They  are  uncomfortable  for 
the  travelling  public,  spoil  the  beauty  of  the  road,  and  help  to 
destroy  it.  3.  Care  should  be  taken  to  fill  all  the  hollows  and 
depressions  in  the  centre,  made  by  the  horses'  feet,  in  order  to 
avoid  having  water  remain  on  the  surface.  If  the  gravel  becomes 
saturated  and  soft,  it  wears  more  rapidly  and  will  soon  rut.  It  is 
important  that  the  crown  of  the  road  should  be  preserved  and 
that  water  should  not  be  allowed  to  run  down  the  centre,  but 
should  have  an  unobstructed  flow  to  the  side  ditches.  In  cases 
where  the  centre  has  been  worn  hollow  the  crown  should  be 
restored  by  adding  the  proper  amount  of  suitable  material. 
This  work  should  be  done  when  the  road  is  wet  and  soft  and  the 
gravel  will  easily  compact  and  bind  together."  4.  The  ditches 
and  culverts  should  be  kept  free  from  obstructions  at  all  times, 
to  secure  an  easy  flow  of  water. 

Maintenance  of  this  nature  may  best  be  accomplished  by 
careful  and  constant  supervision,  aided  by  the  use  of  an  ordinary 
garden  rake,  to  remove  the  larger  pebbles  and  to  smooth  the 
surface.  After  the  road  has  become  compacted  such  constant 
attention  will  not  be  so  necessary. 

REPAIRS  differ  from  maintenance  in  that  they  are  more  ex- 
tensive in  character,  the  surface  having  to  be  practically  rebuilt. 
This  should  be  accomplished  by  the  application  of  one  or  more 
layers  of  gravel,  two  inches  thick,  as  a  greater  thickness  does  not 
pack  or  bind  so  quickly. 

One  of  the  chief  advantages  of  gravel  roads  is  that  they  are 
so  easily  repaired.  Unlike  dirt  roads,  gravel  highways  may  be 
repaired  in  the  fall  without  either  hindrance  to  traffic  or  injury  to 
the  road.  The  gravel,  except  in  very  extensive  and  complete  re- 
pairs, should  be  applied  in  patches  rather  than  in  great  stretches, 
and  then  in  small  quantities  as  it  will  much  more  readily  combine 


GRAVEL   ROADS  55 

with  the  old  surface,  and  at  the  same  time  offer  less  obstruction 
to  traffic.  This  application  may  be  continued  until  the  entire 
road  has  been  covered. 

The  material  used  for  repairs  should  not  be  that  which  is 
taken  from  paring  down  the  shoulders  or  that  which  has  been 
washed  to  the  sides,  but  rather  new  material  kept  for  that 
particular  purpose.  Repairs  with  loam,  sand,  etc.,  are  bad  be- 
cause such  material  only  serves  to  put  the  surface  in  a  sandy  or 
miry  condition.  The  shoulders  should  always  be  kept  true  to  the 
section  and  the  gutters  kept  open. 

For  gravel  roads,  perhaps  more  than  any  other,  the  method  of 
continuous  repairs  is  the  most  advisable. 

GRAVEL  vs.  MACADAM.  "No  just  comparison  can  be  made 
between  gravel  roads  and  macadam,  as  at  no  time  is  a  gravel 
road  in  a  condition  to  give  first-class  results.  Suppose  a  2-horse 
load  of  gravel  delivered  on  the  road  costs  from  $1  to  $1.25  a  load 
of  about  1J  ins.  cu.  yds.  A  road  made  about  6  in  depth  at  this 
price  should  cost  from  20  to  25  cents  per  sq.  yd.  More  or  less  new 
gravel  has  to  be  put  on  each  year,  and  it  is  safe  to  say  that  at  the 
end  of  each  5  years  an  amount  equal  to  the  original  depth  has 
been  used.  This  makes  the  total  cost  about  4  to  5  cents  per  sq. 
yd.,  annually.  If  a  macadam  road  be  built  of  broken  stone 
costing  $2.15  per  cu.  yd.  of  metal  on  the  road  including  rolling,  the 
cost  per  sq.  yd.  would  be  about  47  cents.  A  road  built  in  such 
a  manner  would  easily  withstand  the  traffic  common  to  localities 
removed  from  the  business  centres  for  20  years,  with  slight  re- 
pairs during  that  time.  This  would  make  the  annual  cost  per 
sq.  yd.  about  2J  cents.  By  these  estimates  the  macadam  road 
in  a  term  of  20  years  will  cost  from  about  If  cents  to  2f  cents 
per  sq.  yd.  less  annually  than  the  gravel  road." 

The  following  specifications  for  gravel  roads,  taken  from 
the  Annual  Report  of  the  Commissioner  of  Public  Roads  for  the 
State  of  New  Jersey,  and  indicating  the  practice  existing  in  that 
State,  are  well  worthy  of  consideration. 


56  HIGHWAY   ENGINEERING 

STANDARD    STATE    AID    SPECIFICATIONS    FOR 
GRAVEL    ROADS 

FOR  A  GRAVEL  ROAD  IN COUNTY,  NEW 

JERSEY  KNOWN  AS 

BEGINNING   AT AND 

EXTENDING  TO .» 

A   DISTANCE   OF.  .  , FEET,    OR MILES. 

GRAVEL FEET  WIDE INCHES  DEEP. 

SHOULDERS FEET  WIDE.    TOTAL  WIDTH  OF  ROAD.  . .  .FEET. 

WORK  TO  BE  PERFORMED 

1.  The  work  to  be  performed  will  consist  in  furnishing  all 
material,  tools,  machinery,  and  labor  necessary  for  the  efficient 
and  proper  grading  of  roadway,  side  ditches,  and  side  banks, 
laying,  spreading,  and  rolling  of  road  material,  and  leaving  the 
roadway  complete  in  every  manner  ready  for  immediate  use. 

PLANS   AND    DRAWINGS 

2.  The  plan,  profile,  and  cross-sections  on  file  in  the  office  of 
the  State  Commissioner  of  Public  Roads  and  at  the  office  of .... 

County    Engineer, New    Jersey,    show 

general  location,  profile,  details,  and  dimensions.     The  work  will 
be  constructed  in  all  respects  according  to  the  above-mentioned 
plan,  profile,  and  cross-sections,  which  form  part  of  these  specifi- 
cations. 

3.  Any  variation  of  location,  profile,  size,  and  dimensions  from 
that  shown  on  the  plan,  as  may  be  required  by  the  exigencies  of 
construction,  will,  in  all  cases,  be  determined  by  the  engineer, 
but  the  contractor  shall  not,  on  any  pretence,  save  that  of  the 
written  order  of  the  contracting  parties  and  the  State  Commis- 
sioner of  Public  Roads,  deviate  from  the  intent  of  the  plan  or 
specifications. 


GRAVEL   ROADS  57 

4.  On  all  drawings  figured  dimensions  are  to  govern  in  cases  of 
discrepancy  between  scale  and  figures. 

GRADING 

5.  Under  this  head  will  be  included  all  excavations  and  em- 
bankments required  for  the  formation  of  the  highway,  cutting 
all  ditches  or  drains  about  or  contiguous  to  the  road,  removing 
all  fences,  walls,  buildings,  trees,  poles,  or  other  encumbrances, 
the  excavation  and  embankment  necessary  for  reconstructing 
cross  or  branch  roads  or  entrances  to  dwellings  in  cases  where 
they  are  destroyed  or  interfered  with  in  the  formation  of  the 
roadway,   and  all  other  excavations   and  embankments  con- 
nected with  or  incidental  to  the  construction  of  the  said  road. 

EXCAVATION 

6.  The  roadway  to  the  width  of feet  as  shown 

on  plan  must  be  excavated  or  built  to  the  same  curvature  as  that 
of  the  surface  of  the  road  when  finished ;  the  grade,  from  centre 
to  sides,  must  be  as  shown  on  plans. 

7.  The  earth  taken  from  any  cut  or  ditch  shall  be  deposited 
where  the  engineer  may  direct,  either  within  or  without  the  lines 
of  the  road,  but  no  earth  shall  be  removed  from  the  line  of  the 
road  without  the  order  of  the  engineer. 

EMBANKMENT 

8.  Material  taken  from  the  excavations,  except  when  other- 
wise directed  by  the  engineer,  shall  be  deposited  in  the  embank- 
ments, either  on  the  roadway  or  sidewalks. 

9.  When  there  is  not  sufficient  material  in  the  excavations 
of  the  road  to  form  the  embankments,  the  deficiency  must  be 
supplied  by  the  contractor  from  without  the  road.    The  character 
of  said  material  and  place  of  excavation  must  be  approved  by  the 
engineer. 

10.  The  embankments  must  be  formed  in  layers  of  such  depth, 


58  HIGHWAY   ENGINEERING 

generally  twelve  (12)  inches,  and  the  material  deposited  and  dis- 
tributed in  such  manner  as  the  engineer  may  direct,  the  required 
allowance  for  settling  being  added.  Each  layer  must  be  carried 
across  the  entire  width  of  the  embankment  and  completed  before 
commencing  another,  and  this  method  shall  be  followed  with 
each  succeeding  layer  until  the  established  grade  is  reached. 

SLOPES 

11.  Slopes  in  both  embankment  and  excavation  shall  be  one 
and  one-half  (1J)  horizontal  to  one  (1)  vertical,  when  the  width 
of  the  road  will  permit;  if  the  road  is  too  narrow  to  allow  the 
full  slope  within  its  side  lines,  the  engineer  shall  not  calculate  the 
quantities,  either  in  embankment  or  excavation,  beyond  said  side 
lines,  unless  the  required  ground  shall  be  first  dedicated  to  the 
public  in  writing  by  the  owner  or  owners  thereof. 

ROADWAY 
Subf&undations 

12.  When  the  excavations  and  embankments  have  been 
brought  to  a  proper  depth  below  the  intended  surface  of  the 
roadway,  the  cross-section  conforming  in  every  respect  to  the 
cross-section  of  the  road  when  finished,  the  same  shall,  if  ordered 
by  the  engineer,  be  rolled  until  approved  by  him.     If  any  de- 
pressions form  under  such  rolling,  owing  to  improper  material  or 
vegetable  matter,  the  same  shall  be  removed  and  good  earth  sub- 
stituted, and  the  whole  re-rolled  until  thoroughly  solid  and  to 
above-mentioned  grade. 

SHOULDERING 

13.  A  shoulder  of  firm  earth  or  gravel  is  to  be  left  or  made  on 
each  side  of  the  gravel  bed,  extending  at  the  same  grade  and 
curvature  of  road  to  side  ditches  or  gutters.     This  shoulder  is  to 
be  rolled  according  to  the  directions  of  the  engineer. 


GRAVEL  ROADS  59 

UNDERDRAINS 

14.  Underdrains,  if  found  necessary,  shall  be  constructed  by 
the  contractor  (at  prices  named  in  bids)  of  good  inch 

tile,  laid  upon  a  board  of  not  less  than  one  (1)  inch  in 
thickness  and  six  (6)  inches  in  width,  whenever  and  wherever  the 
engineer  shall  decide ;  top  of  tile  or  pipe  must  be  at  least 
inches  deep,  unless  otherwise  directed  by  the  engineer;  the 
joints  of  the  tile  or  pipe  must  be  covered  with  salt  hay,  or  material 
equally  as  good,  and  trench  filled  with  pervious  earth.' 

15.  When  directed  by  the  engineer  a  stone  drain  may  be  used 
in  place  of  the  tile  drains.     A  trench  one  foot  in  width  and  one 
foot  six  inches  in  depth  shall  be  excavated  below  the  subgrade, 
said  excavation  to  be  filled  with  loose  broken  stone  to  a  depth 
required  by  the  engineer. 

MATERIALS 

16.  The  material  to  be  used  in  surfacing  the  road  is  to  be  fur- 
nished by  the  contractor. 

17.  The  Road  Committee,  in  conjunction  with  the  engineer 
and  State  Commissioner  of  Public  Roads,  will  pass  upon  and  ap- 
prove all  gravel  to  be  used  in  surfacing  the  road.     The  contractor 
is  to  dig,  cart,  and  place  upon  the  road,  in  accordance  with  the 
specifications,  the  gravel  selected  and  use  no  other.     Should  any 
objectionable  material  be  used,  he  is  to  remove  the  same  at  his 
own  expense. 

18.  The  contractor  must  furnish  to  the  engineer  and  State 
Commissioner  of  Public  Roads  samples  of  the  kind  of  gravel  to  be 
used  in  the  work  before  the  opening  of  the  bids. 

19.  The  gravel  is  to  be  placed  upon  the  road  in  such  manner  as 
shall  be  approved  by  the  engineer,  and  be  thoroughly  rolled  and 
solidified  until  it  is  consolidated,  firm,  and  approved  by  the 
engineer.     The  gravel  shall  be  of  such  thickness  that  when  it  is 
thoroughly  compacted  and  approved,  it  shall  be  inches 


60  HIGHWAY   ENGINEERING 

deep  in  the  centre  and  slope  at  a  regular  grade  to 

inches  in  depth  at  a  distance  of  feet  on  each  side  of  the 

centre  line. 

20.  Should  any  depressions  appear  these  are  to  be  carefully 
filled  with  gravel,  so  that  the  finished  road  will  conform  to  the 
approved  profile. 

21.  The  contractor  is  to  be  paid  by  the  cubic  yard,  as  per 
depths  above  named,  for  the  compacted  gravel  that  he  puts  on 
the  road,  at  the  price  named  in  the  accepted  bid,  which  shall  in- 
clude finishing  the  road  and  shaping  the  shoulders  as  above 
specified, 

22.  The  contractor  is  to  place  sufficient  gravel  on  the  road  to 
allow  it  to  shrink  thirty-three  per  cent  in  rolling  and  settling. 

SIDEWALKS 

23.  The  contractor  will  also  be  required,  when  the  engineer  so 
directs,  to  grub  and  remove  from  a  strip  of  land  feet  on 
outside  of  curb-lines  all  material  objectionable  to  the  engineer, 
such  as  trees,  stumps,  roots,  and  brush,  and  refill  the  holes  with 
earth,  thereby  completing  the  opening  of  the  entire  road  to  a 
width  of               feet,  which  shall  be               feet  on  each  side 
of  the  centre  line. 

24.  The  grubbing  and  removing  of  such  objectionable  ma- 
terial that  is  ordered  by  the  engineer  shall  be  styled  as  "  grub- 
bing," and  paid  for  by  the  acre  at  price  named  in  accepted  bid. 

OPEN    DITCHES 

25.  The  contractor  is  to  grade  the  shoulders  and  open  all 
necessary  side  ditches  (as  per  stakes  furnished  by  the  engineer) 
so  that  there  will  be  no  water  allowed  to  stand  by  the  side  of  the 
road  or  upon  it,  for  which  no  extra  payment  will  be  allowed. 

EXTRA   DEEP 

26.  Should  the  engineer  and  State  Commissioner  of  Public 
Roads  so  order,  the  contractor  is  to  build  in  all  respects,  as  al- 


GRAVEL  ROADS  61 

ready  specified,  the  gravel  bed  to  a  greater  depth  or  thickness 
than  that  already  named.  The  contractor  is  to  do  the  same  at  a 
price  named  per  square  yard  for  each  extra  inch  in  depth. 

NO    EXTRA    PRICE 

27.  No  allowance  in  measure  of  depth  of  pavement  will  be 
made  on  account  of  any  material  which  may  be  driven  into  the 
roadbed  by  rolling.     The  pavement,  when  completed,  must  con- 
form to  the  grade  and  cross-section,  and  be  satisfactory  to  the 
engineer  and  State  Commissioner  of  Public  Roads,  whose  decision 
shall  be  final. 

28.  No  extra  work  will  be  paid  for  unless  the  price  has  been 
agreed  upon  between  the  contracting  parties,  including  the  State 
Commissioner  of  Public  Roads,  and  endorsed  upon  the  agree- 
ment, witnessed  by  the  engineer. 

BROAD- TIRE   WAGONS 

29.  All  wagons  and  carts  used  during  the  construction  for 
hauling  stone,  earth,  or  any  other  material  must  have  tires  not 
less  than  three  and  one-half  (3J)  inches  in  width. 

BIDS 

30.  Bids  will  be  received  under  these  specifications  for  the 
road  complete  as  follows : 

(1)  Price  per  cubic  yard  for  earth  excavation,  without  classi- 
fication, as  per  plans  and  cross-sections  throughout  the  length 
and  width  of  the  road. 

(2)  Price  per  acre  for  grubbing  and  removing  objectionable 
material  from  sidewalks. 

(3)  Price  per  lineal  foot  for  completed  tile  drain. 

(4)  Price  per  cubic  yard  for  compacted  gravel  as  specified. 

(5)  Price  per  square  yard  for  each  ordered  inch  in  depth  in 
excess  of  thickness  named. 

(6)  Price  (lump)  for  the  whole  road  complete,  according  to 
the  specifications  and  plans  prepared  by  the  engineer. 


62  HIGHWAY  ENGINEERING 

No  bid  will  be  received  in  which  all  the  above  items  are  not 
filled  out. 

ESTIMATE   OF  QUANTITIES 

31.  (1)  Earth  excavation cubic  yards. 

(2)  Grubbing acres. 

(3)  The  drain lineal  feet. 

(4)  Compacted  gravel cubic  yards. 

Total  estimated  cost  of  the  road,  $ .... 

32.  These  quantities  are  the  result  of  calculation,  but  are  to 
be  considered  as  approximate.     The  county  will  not  be  respon- 
sible for  any  excess  in  above  quantities,  should  any  occur. 
The  contractor  is  expected  to  satisfy  himself  by  a  personal  ex- 
amination of  the  work  contemplated,  about  the  nature,  character, 
and  quantity  of  the  labor  and  material  required. 

CHECK   ACCOMPANYING   BIDS 

33.  Bids  shall  be  accompanied  with  a  certified  check,  payable 
to  the  Director  of  the  Board  of  Chosen  Freeholders,  for  the  sum 
of  one  thousand  dollars  ($1,000),  as  a  guaranty  that  if  the  con- 
tract shall  be  awarded  to  him  he  will,  when  required  by  said 
Board,  execute  an  agreement  in  writing  to  perform  the  work 
according  to  the  specifications,  and  upon  failure  by  the  con- 
tractor to  enter  into  said  agreement  with  the  said  Board  of  Chosen 
Freeholders,  said  certified  check  shall  be  forfeited  and  considered 
as  liquidated  damages. 

LIABILITIES   OF   CONTRACTOR 

34.  He  shall  keep  up  sufficient  guards  by  day  and  night  to 
prevent  accidents  from  travel,  and  will  be  liable  for  any  damage 
which  may  arise  from  his  neglect  to  do  so,  or  from  any  omission 
on  his  part. 

35.  He  is  to  commence  and  prosecute  the  work  upon  the  road 
at  such  points  as  may  be  directed  by  the  engineer,  within 


GRAVEL   ROADS  63 

days  from  and  after  the  signing  of  the  contract,  and  shall  con- 
tinue work  thereon  until  completion,  except  as  herein  provided. 

36.  He  further  agrees  to  complete  the  same  on  or  before  the 

day  of  A.D. 

37.  Twenty  dollars  for  each  day  that  the  work  shall  remain 
uncompleted,  after  the  time  allowed  by  contract,  may  be  de- 
ducted, as  liquidated  damages,  from  any  moneys  due  contractor, 
unless  otherwise  agreed  upon  by  the  Board. of  Chosen  Freeholders 
after  presentation  of  certificate  of  the  engineer  recommending  the 
extension  of  the  time  limit  of  completion. 

38.  The  contractor  shall  keep  the  finished  roadway,  earth- 
work, side  ditches,  and  underdrains  in  repair  for  the  period  of  one 
year  from  the  date  of  its  completion  and  acceptance,  and,  in 
addition  thereto,  for  as  much  longer  as  for  any  period  or  periods 
during  said  year  it  shall  be  out  of  proper  condition.     If,  during 
that  time,  the  roadway  or  any  part  of  the  work  shall,  in  the  judg- 
ment of  the  engineer  and  the  Board  of  Chosen  Freeholders,  re- 
quire repairing,  and  they  shall  duly  notify  the  contractor  to  make 
such  repairs  as  required,  and  the  contractor  should  refuse  or 
neglect  to  do  so  to  the  satisfaction  of  the  said  engineer  and  Board 
of  Chosen  Freeholders,  within  five  days  from  the  date  of  service  of 
notice,  then  the  said  engineer  and  Board  of  Chosen  Freeholders 
shall  have  the  right  to  have  the  work  done  properly  by  other 
parties  and  recover  the  cost  for  the  same  from  the  said  contractor 
or  his  surety. 

39.  The  contractor  will  be  required  to  preserve  all  stakes  and 
bench-marks  made  and  established  on  the  line  of  work  until  duly 
authorized  by  the  engineer  to  remove  the  same. 

40.  The  contractor  shall  not  disturb  the  position  of  title- 
stones  (the  corners  of  properties  adjacent  to  the  road),  but  where 
they  appear  he  will  either  lift  or  lower  them,  under  the  per- 
sonal supervision  of  the  engineer. 

41.  The  contractor  must  also  preserve  the  roadway  on  which 
he  is  working  from  needless  obstruction,  and  where  necessary 


64  HIGHWAY   ENGINEERING 

construct  safe  and  commodious  crossings,  to  be  maintained  in 
good  order.  He  shall  afford  all  proper  and  reasonable  means  for 
the  accommodation  of  the  public,  and  leave  the  roadway  com- 
plete in  every  manner  ready  for  immediate  use. 

42.  All  loss  or  damage  arising  from  the  nature  of  the  work  to 
be  done,  or  from  any  unforeseen  or  unusual  obstruction  or  dif- 
ficulty, which  may  be  encountered  in  the  prosecution  of  said 
work,  or  from  the  action  of  the  elements,  shall  be  sustained  by 
the  contractor. 

PROVISION    FOR   DRAINAGE 

43.  If  it  is  necessary  in  the  prosecution  of  the  work  to  in- 
terrupt or  obstruct  the  natural  drainage  of  the  surface,  or  the 
flow  of  artificial  drains,  the  contractor  shall  provide  for  the  same 
during  the  progress  of  the  work  in  such  a  way  that  no  damage 
shall  result  to  either  public  or  private  interests.     He  shall  be 
held  liable  for  all  damages  which  may  result  from  any  neglect  to 
provide  for  either  natural  or  artificial  drainage,  which  he  may 
have  interrupted. 

RIGHT  TO  BUILD   BRIDGES,   CULVERTS,   ETC.,   AND  SUSPENSION  OF 

WORK 

44.  The  right  of  the  county  to  build  bridges,  culverts,  lay 
pipes  or  other  appurtenances  in  said  road  during  the  progress  of 
the  work  is  expressly  reserved,  as  well  as  suspending  the  work, 
or  any  part  thereof,  during  the  construction  of  the  same,  for  the 
purposes  above  stated,  without  further  compensation  to  the 
contractor  for  such  suspension  than  an  extension  of  time  for 
completing  the  work  as  much  as  it  may  have  been  delayed. 

STOPPING   WORK   ON   ACCOUNT   OF   WEATHER 

45.  The  State  Commissioner  of  Public  Roads,  engineer,  or 
supervisor  may  stop  any  portion  of  the  work  if,  in  their  judgment, 
the  weather  is  such  as  to  prevent  the  same  being  done  properly. 


GRAVEL   ROADS  65 

No  allowance  of  any  kind  will  be  made  for  such  stoppage,  except 
an  extension  of  the  time  for  the  completion  of  the  work  as  herein 
provided. 

ABANDONMENT   OF   CONTRACT 

46.  If  at  any  time  the  work  under  contract  should  be  aban- 
doned, or  if  at  any  time  the  engineer  should  judge  and  so  certify 
in  writing  that  said  work,  or  any  part  thereof,  is  unnecessarily 
delayed,  or  that  the  contractor  is  wilfully  violating  any  of  the 
conditions  or  covenants  of  this  contract,  or  is  executing  the  same 
in  bad  faith,  then,  and  in  that  case,  the  Board  of  Chosen  Free- 
holders shall  notify  the  said  contractor  to  discontinue  all  work 
under  this  contract.     It  may  employ  other  parties  to  complete 
the  work  in  such  manner  as  it  may  decide,  and  use  such  material 
as  may  be  procured  upon  the  line  of  aforesaid  work,  and,  if  neces- 
sary, to  procure  other  material  for  its  completion,  and  charge  the 
expense  of  the  said  labor  and  material  to  the  contractor,  which 
expense  shall  be  deducted  from  any  moneys  due  him  under  con- 
tract.    In  case  these  expenses  shall  exceed  the  sum  which  would 
have  been  payable  under  contract,  if  the  same  had  been  com- 
pleted by  said  contractor,  he  or  his  bondsmen  shall  pay  the 
amount  of  the  excess  to  the  Board  of  Chosen  Freeholders,  on  no- 
tice from  the  engineer. 

ENGINEER 

47.  The  engineer  shall  be  selected  or  appointed  by  the  Board 
of  Chosen  Freeholders  and  paid  by  it.     He  shall  furnish  all  sur- 
veys, profiles,  plans,  specifications,  and  estimates  of  quantities 
of  all  kinds  before  specifications  are  signed,  and  in  such  a  clear 
manner  that  lump  bids  can  be  made  upon  the  work.     He  shall 
furnish  all  lines  and  grades  required  for  the  completion  of  the 
work.     He  shall  furnish  estimates  for  quantities  of  work  done 
before  partial  payments  can  be  made,  the  quantity  of  road  laid 
being  determined  by  surface  measurements.     Should  any  dif- 
ference arise  between  the  contracting  parties  as  to  the  meaning 

5 


66  HIGHWAY   ENGINEERING 

or  intent  of  these  specifications,  his  decisions  on  these  matters 
are  to  be  final  and  conclusive.  The  work  is  to  be  done  according 
to  his  directions,  and  if  any  material  of  which  he  does  not  approve 
is  brought  upon  the  road  it  is  to  be  removed  at  the  expense  of  the 
contractor.  If  the  contractor  fails  or  neglects  to  do  any  part  of 
the  work  as  specified  or  as  directed  by  the  engineer,  then,  in  that 
case,  all  other  work  shall  be  discontinued,  on  notice  from  the 
engineer  to  the  contractor,  or  to  the  superintendent  or  foreman 
in  charge  of  the  work  for  the  contractor,  until  such  time  as  the 
work  complained  of  has  been  done  to  the  satisfaction  of  the  en- 
gineer, and  the  contractor  will  not  be  entitled  to  or  allowed  any 
compensation  or  extension  of  time  for  such  discontinuation  or 
suspension  of  the  work. 

SUPERVISOR 

48.  Nothing  in  these  specifications  relating  to  the  duties  of 
the  engineer  shall  be  taken  or  construed  in  any  manner  to  con- 
flict with  the  duties  of  the  supervisor,  as  specifically  set  forth  in 
the  act  entitled  "  An  act  to  provide  for  the  permanent  improve- 
ment of  public  roads  in  this  state,"  approved  March  27th,  1905, 
but  they  shall  cooperate  as  far  as  practicable. 

INCOMPETENT   WORKMEN 

49.  The  contractor  shall  employ  competent  men  to  do  the 
work,  and  whenever  the  engineer  and  supervisor  shall  inform 
him,  or  his  representative  in  charge,  in  writing,  that  any  man  on 
the  work  is  unfitted  for  the  place,  or  is  working  contrary  to  the 
provisions  of  the  specifications  or  the  instructions  of  the  engineer 
and  supervisor,  he  shall  thereupon  be  discharged. 

INSPECTION 

50.  All  directions  and  determinations  necessary  to  give  due 
and  full  effect  to  any  of  the  provisions  of  these  specifications  shall 
be  given  by  the  engineer  and  supervisor. 


GRAVEL   ROADS  67 

51.  All  material  and  workmanship  of  any  kind  shall  be  sub- 
ject at  all  times  to  the  inspection  of  the  engineer  and  supervisor. 
Whenever  unfaithful  and  imperfect  work  is  discovered,  it  shall 
be  immediately  repaired  or  replaced  by  the  contractor,  after  due 
notification  from  the  engineer  and  supervisor. 

SUBLETTING   OF   CONTRACT 

52.  The  contractor  shall  not  assign  or  sublet  any  portion  of 
this  contract  without  the  consent  of  the  Board  of  Chosen  Free- 
holders and  the  State  Commissioner  of  Public  Roads. 

PAYMENTS 

53 monthly  payments  will  be  made  by  the 

Board  of  Chosen  Freeholders  to  the  contractor  for  work  per- 
formed, upon  presentation  by  him  of  the  proper  certificates  of  the 
engineer  and  supervisor,  in  a  sum  not  to  exceed  eighty  per  cent 
of  the  amount  then  due,  together  with  releases  from  all  liens, 
if  required.  Fifteen  per  cent  will  be  paid  at  the  completion  of  the 
work  and  the  acceptance  of  the  same  in  writing  by  the  Board  of 
Chosen  Freeholders  and  the  State  Commissioner  of  Public  Roads. 
The  remainder,  or  five  per  cent,  will  be  retained  by  the  Board  of 
Chosen  Freeholders  for  a  period  of  one  year  as  security  for  the 
faithful  performance  of  Article  38. 

BOND   OF   CONTRACTOR 

54.  The  contractor  will  be  required  to  execute,  within  thirty 
days  of  giving  of  contract,  a  bond  in  such  sum  and  with  such 
securities  as  shall  be  approved  by  the  Board  of  Chosen  Free- 
holders, conditioned  for  the  faithful  performance  of  the  contract, 
to  indemnify  and  save  harmless  the  said  Board  of  Chosen  Free- 
holders from  all  suits  or  actions  of  any  name  or  description 
brought  against  them  on  account  of  any  act  or  omission  of  the 
contractor  or  his  agents,  and  for  the  faithful  performance  of  the 
contract  by  the  contractor.  Said  bond  shall  be  in  a  sum  of  not 


68  HIGHWAY   ENGINEERING 

less  than  the  estimated  cost  of  the  road  when  completed.  Any 
change  made  in  said  plans,  specifications,  agreements,  or  quanti- 
ties without  the  consent  of  the  bondsmen  shall  in  no  way  vitiate 
said  bond.  The  said  contractor  hereby  further  agrees  that  so 
much  of  the  money  due  him,  under  and  by  virtue  of  this  agree- 
ment, as  shall  be  considered  necessary  by  the  Board  of  Chosen 
Freeholders,  may  be  retained  by  it  until  all  such  suits  or  claims 
for  damages  aforesaid  shall  have  been  settled,  and  evidence  to 
that  effect  furnished  to  the  satisfaction  of  the  said  Board  of 
Chosen  Freeholders. 

CONTRACTOR  TO  INSURE  PAYMENT  FOR  LABOR,  MATERIAL,  ETC.,  ON 
FINAL   ESTIMATE 

55.  The  contractor  must  also  furnish  said  engineer  with  satis- 
factory evidence  that  all  persons  who  did  work,  or  furnish  material 
for  this  contract,  or  who  have  sustained  damage  or  injury  by 
reason  of  any  act,  omission,  or  carelessness  on  his  part  or  his 
agents  in  the  prosecution  of  the  work,  have  been  duly  paid  or 
secured ;  he  shall  also  give  notice  to  said  engineer  within  ten  days 
after  the  completion  of  the  work,  and  before  final  estimate  is 
made,  that  any  balance  for  such  work  or  materials,  or  compensa- 
tion for  such  damages  due,  has  been  fully  paid  or  released. 

56.  The  right  is  reserved  to  reject  any  or  all  bids,  if  deemed  to 
the  interest  of  the  county  or  State. 


County  Engineer. 

Approved  this day  of ,  A.D.  190    ,  by  reso- 
lution of  the  Board  of  Chosen  Freeholders  of  the  county  of 


Director  of  Board  of  Chosen  Freeholders. 
Clerk  of  Board  of  Chosen  Freeholders. 


GRAVEL  ROADS  .  69 

OFFICE  STATE  COMMISSIONER  OF  PUBLIC  ROADS,  TRENTON, 
N.  J. 

I  have  this  day  carefully  read  and  examined  the  foregoing 
specifications,  and  the  same  are  hereby  approved. 

Any  departure  from  these  specifications' must  have  the  writ- 
ten consent  of  the  State  Commissioner  of  Public  Roads. 

Given  under  my  hand,  this day  of,  A.D 


State  Commissioner  of  Public  Roads. 


CHAPTER  IV 
BROKEN-STONE  ROADS 

DEFINITION.  A  broken-stone  road  is  one  in  which  the  surfac- 
ing material,  resting  upon  an  earth  or  stone  foundation,  is  com- 
posed of  small  fragments  of  crushed  rock,  and  so  consolidated  by 
rolling  or  traffic  as  to  form  a  compact  mass,  with  a  smooth 
and  impervious  surface. 

KINDS.  Such  roads  are  divided  into  two  general  classes, 
Macadam  and  Telford,  receiving  their  names  from  the  English 
engineers  who,  about  the  middle  of  the  eighteenth  century,  were 
instrumental  in  demonstrating  their  superior  qualities.  Both 
types  agree  in  the  use  of  fragments  of  broken  stone,  but  differ 
materially  in  the  foundation  upon  which  it  rests. 

Macadam.  As  originally  built,  a  macadam  pavement  con- 
sisted of  a  layer  of  broken  stone  2J  ins.  in  diameter,  and  8  to  10 
ins.  deep,  laid  for  the  full  width  of  the  roadway.  According  to 
Macadam,  "  The  stone  was  employed  to  form  a  secure,  smooth, 
water-tight  flooring,  over  which  vehicles  might  pass  with  safety 
and  expedition  at  all  seasons  of  the  year.  The  thickness  was 
regulated  only  by  the  quality  of  the  material  necessary  to  form 
such  a  flooring,  and  not  at  all  by  any  consideration  as  to  its  own 
independent  power  of  bearing  weight." 

This  rested  upon  the  natural  soil  as  a  foundation,  particular 
attention  being  given  to  the  matter  of  drainage,  to  prevent  water 
either  remaining  in  the  roadbed  or  flowing  toward  it. 

No  binder  nor  road  roller  was  used  to  help  cement  the  frag- 
ments together,  but  consolidation  depended  entirely  upon  the 
action  of  traffic. 

The  term  "  binder,"  it  should  here  be  stated,  applies  to  any 

70 


BROKEN-STONE    ROADS 


71 


fine  material,  about  one-quarter  inch  in  size  or  smaller,  which  ia 
used  on  a  stone  road  for  the  purpose  of  filling  in  the  interstices, 
between  the  fragments  of  stone  and  cementing  or  binding  them 
together,  so  that  the  covering  may  be  smooth,  compact,  and 
impervious  to  water. 

A  Telf ord  Pavement  differs  materially  from  one  of  macadam, 
being  constructed  as  follows:  "Upon  the  level  bed  prepared  for 


FIG.  23. — Macadam  Pavement  with  Gutter. 

the  road  materials,  a  bottom  course  or  layer  of  stones  is  set,  by 
hand,  in  the  form  of  a  close,  firm  pavement.  The  stones  set  in 
the  middle  of  the  road  should  be  7  ins.  deep;  at  9  ft.  from  the 
centre,  5  ins.  deep;  and  at  15  ft.  from  the  centre,  3  ins.  deep. 
They  should  be  set  upon  their  broadest  edges  lengthwise  across 
the  road,  and  the  breadth  of  the  upper  edge  should  not  exceed 
4  ins.  in  any  case.  All  irregularities  of  the  upper  part  of  the 


FIG.  24.— Telf  ord  Pavement. 

pavement  should  be  broken  off  by  a  hammer,  and  all  interstices 
filled  with  stone  chips  firmly  wedged,  or  packed  by  hand  with  a 
light  hammer,  so  that  when  the  whole  pavement  is  finished  there 
shall  be  a  convexity  of  4  ins.  in  the  breadth  of  15  ft.  from  the 
centre. 

"  The  middle  18  ft.  of  the  pavement  should  be  coated  with 


72 


HIGHWAY  ENGINEERING 


BROKEN-STONE   ROADS 


73 


hard  stone  to  the  depth  of  6  ins.     Four  of  these  6  ins.  to  be  first 
put  on  and  worked  in  by  carriages  and  horses ;  care  being  taken 
to  rake  in  the  ruts  until  the  surface  has  become  firm  and  con- 
solidated, after  which  the  remaining 
2  ins.  may  be  put  on. 

"The  whole  of  this  stone  should 
be  broken  into  pieces  as  nearly  cu- 
bical as  possible,  so  that  the  largest 
piece  in  its  largest  dimensions  may 
pass  through  a  ring  of  2J  ins.  inside 
diameter. 

"The  paved  spaces  on  each  side 
of  the  middle  18  ft.  should  be  coated 
with  broken  stone  or  well-cleaned 
gravel  up  to  the  foot-path  or  other 
boundary  of  the  road  so  as  to  make 
the  whole  convexity  of  the  road  6  ins. 
from  the  centre  to  the  sides  of  it,  and 
the  whole  of  the  materials  is  then 
covered  with  a  binder  of  1J  ins.  of 
good  gravel  free  from  clay  or  earth." 
Modern  Stone  Roads  vary  but 
little  from  the  above  types  and  then 
only  in  the  minor  details,  the  same 
general  principles  governing  their 
construction  and  maintenance  as 
those  laid  by  Macadam  and  Telford. 

Present  practice  requires,  how- 
ever, that  the  foundation  upon 
which  the  stone  is  to  rest  shall  be 
graded  and  thoroughly  consolidated 
by  a  heavy  roller  until  it  conform  in  cross-section  with  that  of 
the  finished  covering.  Should  any  depressions  result  from  this 
process,  they  must  be  filled  with  good  loamy  earth,  and  the 


74 


HIGHWAY   ENGINEERING 


rolling  continued  until  the  soil  is  thoroughly  compacted  and 
true  to  grade. 

In  modern  telford  pavements,  "  after  the  roadbed  has  been 
rolled,  a  bottom  course  of  stone  is  set  by  hand  as  a  close  firm 
pavement,  the  stones  being  placed  on  their  broadest  edges,  length- 
wise across  the  road  in  such  manner  as  to  break  joints  as  much  as 
possible,  the  breadth  of  the  upper  edge  not  to  exceed  4  ins." 
No  stones  larger  than  10  ins.  long  by  4  ins.  wide  may  be  used. 
This  foundation  course  is  settled  by  ramming  or  rolling,  and  upon 


FIG.  28. — Standard  Sections  in  Cut  and  Fill,  as  Built  in  Madison  Co.,  Tenn. 

it  placed  the  successive  layers  of  smaller  stone  as  in  a  macadam 
pavement. 

In  modern  macadam,  the  roadbed  is  prepared  as  above, 
but  instead  of  a  foundation  being  put  down,  the  broken  stone  is 
laid  directly  upon  the  earth.  The  first  layer  of  stone  consists 
of  two  and  one-half-inch  fragments,  or  that  passing  a  three-inch 
Ting,  deposited  to  the  required  depth,  and  repeatedly  rolled 
Until  consolidation  takes  place. 


o 

o 

1 


I 


.3 

— 

fi 
g, 

I 


BROKEN-STONE   ROADS  81 

Over  the  first  course  binder  may  be  spread  and  rolled  until  it 
has  worked  into  the  interstices  and  the  stones  cease  to  creep  or 
sink  before  the  roller.  A  second  course  of  1J  in.  stone  is  laid  on 
this,  and  treated  as  in  the  above.  Upon  this  finally  is  laid  a  coat 
of  50  per  cent  f  in.  stone;  and  50  per  cent  screenings  well  mixed, 
which  is  again  subjected  to  rolling. 

TESTS  ON  ROAD  STONE.  The  following  abstract,  substan- 
tially as  it  appeared  in  an  article  on  "  Current  Practice  in  Labora- 
tory Tests  of  Road  Materials,"  by  Prof.  A.  Black,  indicates  the 
method  of  making  tests  on  road  stone  to  determine  its  suitability 
to  such  purposes. 

The  qualities  required  in  a  good  road  stone  are  hardness, 
toughness,  and  binding  or  cementing  properties  of  the  finer  abraded 
material;  also,  to  a  less  extent,  the  ability  to  resist  the  disinte- 
grating action  of  the  weather,  and,  probably,  of  some  organic 
acids  produced  by  the  decomposition  of  excretal  matters  always 
present  upon  roadways  in  use. 

"  By  hardness  is  meant  the  power  possessed  by  a  rock  to  re- 
sist the  wearing  action  caused  by  the  abrasion  of  wheels  and 
horses'  feet.  Toughness,  as  understood  by  road  builders,  is  the 
adhesion  between  the  crystals  and  fine  particles  of  a  rock,  which 
gives  it  power  to  resist  fracture  when  subjected  to  the  blows  of 
traffic.  This  important  property,  while  distinct  from  hardness, 
is  yet  intimately  associated  with  it,  and  can,  in  a  measure,  make 
up  for  a  deficiency  in  hardness.  Hardness,  for  instance,  would 
be  the  resistance  offered  by  a  rock  to  the  grinding  of  an  emery 
wheel ;  toughness  the  resistance  to  fracture  when  struck  with  a 
hammer. 

"  Cementing  or  binding  power  is  the  property  possessed  by  the 
dust  of  a  rock  to  act  after  wetting  as  a  cement  to  the  coarse  frag- 
ments composing  the  road,  binding  them  together  and  forming  a 
smooth,  impervious  shell  over  the  surface.  Such  a  shell,  formed 
by  a  rock  of  high  cementing  value,  protects  the  underlying 
material  from  wear  and  acts  as  a  cushion  to  the  blows  from  horses' 
6 


82  HIGHWAY   ENGINEERING 

feet,  and  at  the  same  time  resists  the  waste  of  material  caused  by 
wind  and  rain,  and  preserves  the  foundation  by  shedding  the 
surface  water.  Binding  power  is  thus  probably  the  most  im- 
portant property  to  be  sought  for  in  a  road-building  rock,  as  its 
presence  is  always  necessary  for  the  best  results. 

"  The  hardness  and  toughness  of  the  binder  surface,  more  than 
of  the  rock  itself,  represents  the  hardness  and  toughness  of  the 
road,  for  if  the  weight  of  traffic  is  sufficient  to  destroy  the  bond  of 
cementation  of  the  surface,  the  stones  below  are  soon  loosened 
and  forced  out  of  place.  When  there  is  an  absence  of  binding 
material,  which  often  occurs  when  the  rock  is  too  hard  for  the 
traffic  to  which  it  is  subjected,  the  road  soon  loosens  or  ravels. 

"  Experience  shows  that  a  rock  possessing  all  three  of  the 
properties  mentioned  in  a  high  degree  does  not  under  all  con- 
ditions make  a  good  road  material;  on  the  contrary,  under  cer- 
tain conditions  it  may  be  altogether  unsuitable.  As  an  illus- 
tration of  this,  if  a  country  road  or  a  city  parkway,  where  only  a 
light  traffic  prevails,  were  built  of  a  very  hard  and  totigh  rock 
with  a  high  cementing  value,  neither  the  best,  nor,  if  a  softer  rock 
were  available,  would  the  cheapest  results  be  obtained.  Such 
a  rock  would  so  effectively  resist  the  wear  of  a  light  traffic  that 
the  amount  of  fine  dust  worn  off  would  be  carried  away  by  wind 
and  rain  faster  than  it  would  be  supplied  by  wear.  Conse- 
quently, the  binder  supplied  by  wear  would  be  insufficient,  and 
if  not  supplied  from  some  other  source  the  road  would  soon  go  to 
pieces.  The  first  cost  of  such  a  rock  would  in  most  instances  be 
greater  than  that  of  a  softer  one,  and  the  necessary  repairs 
resulting  from  its  use  would  also  be  very  expensive.  .  .  . 

"  The  degree  to  which  a  reck  absorbs  water  may  also  be  im- 
portant, for  in  cold  climates  this  to  some  extent  determines  the 
liability  of  a  rock  to  fracture  by  freezing.  It  is  not  so  important, 
however,  as  the  absorptive  power  of  the  road  itself,  for  if  the  road 
holds  much  water  the  destruction  wrought  by  frost  is  very  great. 
This  trouble  is  generally  due  to  faulty  construction  rather  than 


BROKEN-STONE    ROADS  91 

to  material.  The  density  or  weight  of  a  rock  is  also  considered 
of  importance,  as  the  heavier  the  rock  the  better  it  stays  in  place 
and  the  better  it  resists  the  action  of  wind  and  rain." 

These  qualities  are  seldom  found  together  in  the  same  stone. 
Igneous  and  silicious  rock,  although  frequently  hard  and  tough, 
do  not  consolidate  so  well,  nor  so  quickly,  under  the  traffic  as 
limestone,  owing  to  the  fact  that  the  sandy  detritus  formed  by 
such  rocks  has  no  cohesion ;  while  the  limestone  yields  a  fine 
material  which  acts  like  mortar  in  binding  the  individual  stones 
together.  A  stone  with  good  binding  properties  will  frequently 
wear  much  better  than  a  harder  and  tougher  material  deficient 
in  such  properties.  The  engineer,  therefore,  is  often  called 
upon,  in  selecting  a  road  material,  to  make  a  judicious  com- 
promise between  the  different  requisite  characteristic  properties 
of  a  first-class  roadway,  to  suit  the  particular  conditions  and  the 
special  problems  presented;  and  it  is  the  object  of  the  testing 
laboratories  to  furnish  him  with  the  necessary  data  for  this 
purpose. 

Resistance  to  Abrasion.  The  apparatus  used  for  this  test  is 
essentially  the  old  Deval  machine  used  in  France  since  1878  or 
earlier.  In  its  original  form  it  consisted  of  2  iron  cylinders, 
each  20  cm.  in  diameter,  and  34  cm.  long,  interior  measurements. 
Each  cylinder  was  closed  on  one  end,  and  had  a  specially  fitted 
cover  on  the  other,  which,  by  means  of  a  leather  gasket,  could  be 
bolted  on  air-tight.  The  cylinders  were  attached  to  a  horizontal 
shaft,  to  which  they  were  inclined  at  an  angle  of  30  degrees 
and  about  which  they  were  rotated  by  means  of  a  pulley  wheel 
fastened  to  the  shaft. 

The  abrasion  machines  of  to-day  are  essentially  as  that  de- 
scribed above,  except  that  there  are  four  cylinders  on  the  same 
shaft,  so  that  it  is  possible  to  make  four  abrasion  tests  simultane- 
ously. A  counter  is  used  for  recording  the  number  of  revolu- 
tions. Fig.  36. 

The  material  to  be  tested  is  broken  into  pieces  from  one  and 


92  HIGHWAY    ENGINEERING 

one-fourth  to  two  and  one-half  inches  in  diameter,  the  sizes  usu- 
ally employed  on  roadways,  and  as  nearly  cubical  as  is  practicable 
with  the  appliances  ordinarily  used  for  sucli  work.  These  stones 
should  be  thoroughly  washed  and,  if  necessary,  scrubbed,  to 
remove  all  dust  and  foreign  matter;  and  should  then  be  allowed 
to  dry  for  several  days  before  being  used.  Five  kilograms  of  the 
clean  broken  stone,  accurately  weighed,  constitute  the  charge 
for  each  cylinder.  The  cylinders  being  charged,  the  covers  are 
bolted  on  securely,  and  the  shaft  rotated  at  the  rate  of  2,000  revo- 
lutions per  hour,  for  five  hours.  Each  rotation  throws  the  pieces 


FIG.  36. — Abrasion  Machine  for  Macadam  Material, 
of  stone  twice  from  one  end  of  the  cylinder  to  the  other,  causing 
them  to  grind  against  one  another  and  against  the  sides  and  ends 
of  the  cylinders. 

When  the  counter  has  recorded  10,000  revolutions,  the 
machine  is  stopped,  the  covers  unbolted,  and  the  contents  care- 
fully scraped  and  brushed  out  of  the  cylinders  into  the  upper  of  2 
superimposed  sieves,  having  16  and  100  meshes  to  the  linear  inch 
respectively.  These  sieves  rest  on  the  edge  of  a  broad  pan  which 
receives  all  that  passes  through  them. 

The  material  retained  on  the  upper,  or  coarser,  sieve  is  thor- 
oughly washed,  and  then  put  aside  to  dry  for  about  two  days.  It 
is  then  carefully  weighed,  its  weight  deducted  from  the  original 
cylinder  charge,  and  the  difference  recorded  as  loss  due  to  abra- 
sion; for  it  has  been  agreed  to  consider  as  abraded  all  that  passes 
the  sieve  with  sixteen  meshes  to  the  linear  inch ;  while  the  larger 


BROKEN-STONE   ROADS  93 

particles  retained  on  that  sieve  are  assumed  to  be  the  original 
pieces  reduced  by  wear,  or  broken  into  smaller  pieces  by  impact. 

This  simple  method,  by  differences,  of  determining  the  abra- 
sion loss  should  always  be  used  in  preference  to  the  laborious  and 
not  more  accurate  method,  sometimes  prescribed,  of  weighing 
directly  the  finer  material,  which  involves  the  thorough  washing 
of  the  cylinder  to  remove  the  adhering  dust,  and  the  washing 
of  the  larger  particles  in  the  same  water,  which  must  then  be 
filtered,  the  filtrate,  when  dry,  mixed  with  the  cylinder  detritus 
previously  set  aside,  and  the  mixture  sifted  on  the  sixteen-mesh 
sieve,  the  material  passing  through  this  sieve  being  then 
weighed. 

The  numerical  value  for  the  abrasion  of  the  specimen  may  then 
be  stated  in  either  of  two  ways :  by  the  percentage,  by  weight,  of 
the  original  charge  that  has  been  worn  off  by  abrasion;  or  the 
French  coefficient  of  wear  may  be  used,  which  has  been  developed 
from  the  following  considerations: 

In  the  earlier  French  tests  a  rock  of  superior  wearing  quali- 
ties was  always  placed  in  one  of  the  cylinders  as  a  standard  of 
comparison;  and  the  ratio  of  the  weights  abraded,  in  the  case  of 
the  standard  rock  and  of  the  specimen  under  test,  was  supposed 
to  indicate  their  relative  resistances  to  abrasion.  It  was  soon 
found  that  only  the  best  varieties  of  rock  produced  less  than  20 
gm.  of  abraded  material  per  kilogram  of  original  charge;  the 
number  20  was,  therefore,  adopted  as  a  "  standard  of  excellence/7 
and  the  coefficient  of  wear  for  any  stone  tested  was  obtained  from 
the  formula : 

n        ',          ,  20  X  20       400 

Coefficient  of  wear  = = 

w  w 

in  which  w  represents  the  weight  in  grams  abraded  per  kilogram 
of  original  charge. 

When  the  value  of  the  resistance  to  wear  by  rubbing  is  re- 
quired, the  Dorrey  machine  is  employed.  The  standard  method 
of  the  French  School  of  Roads  and  Bridges  is  as  follows : 


94  HIGHWAY   ENGINEERING 

The  specimens  to  be  tested  are  cut  into  rectangular  prisms,  4 
cm.  by  6  cm.  base,  and  8  cm.  high.  They  are  tested  in  sets  of 
2,  and  are  held  in  clamps  against  the  upper  surface  of  a  circular 
grinding  disk  of  cast  iron,  on  opposite  sides  of,  and  26  cm.  from, 
the  centre.  The  specimens  are  weighted  to  press  against  the 
grinding  disk,  with  a  pressure  of  250  gm.  per  sq.  cm.  Sand, 
obtained  by  crushing  quartzite  and  screening  to  standard  size,  is 
fed  onto  the  disk  through  a  funnel,  allowing  1  litre  of  sand,  per 
specimen,  for  each  1,000  turns.  The  disk  is  rotated  at  the  rate  of 
2,000  revolutions  per  hour,  for  2  hours,  or  4,000  revolutions  for  a 
test. 

After  2,000  revolutions  the  specimens  are  reversed,  to  take  in- 
to account  a  possible  difference  in  texture  in  the  2  parts.  The 
diminution  in  height  is  measured,  and  the  loss  in  weight  deter- 
mined, after  each  1,000  turns  of  the  disk.  Tests  should  be  made 
on  at  least  3  samples  of  each  specimen,  and  their  average 
taken  as  the  final  result.  Usually  the  loss  in  height  after  4,000 
revolutions  is  used  in  comparing  different  road  stones;  and  fre- 
quently a  specimen  of  some  standard  rock,  as  Yvette  sandstone,  is 
placed  on  the  disk  and  tested  with  the  other  specimens,  and  the 
reduction  in  height  referred  to  that  of  the  standard. 

This  method  has  not  come  into  general  use  in  road-material 
laboratories  in  the  United  States. 

The  Cementation  Test. — The  purpose  of  the  cementation  test  is 
to  obtain  the  relative  binding  powers  of  the  various  stones  used  in 
road-making.  Good  binding  power  has  long  been  known  to  road 
builders  to  be  one  of  the  most  important  properties  possessed  by 
a  satisfactory  road  stone.  If  the  fine  material  of  a  road  binds 
well,  it  protects  the  coarser  stones  beneath  from  wear,  withstands 
better  the  action  of  wind  and  rain,  and  prevents  water  from  get- 
ting to  the  foundation  of  the  road.  Cementing  power  is  thus 
seen  to  be  a  very  important  and  valuable  property  of  any  road 
material.  Experiments  had  been  carried  on  for  some  five  years, 
in  the  laboratory  of  the  Massachusetts  Highway  Commission,  to 


BROKEN-STONE   ROADS 


95 


determine  some  way  of  testing  this  important  property.  The 
test  finally  adopted  was  an  impact  test,  to  which  stone-dust  bri- 
quettes are  subjected.  The  method  in  quite  general  use  until 
recently  is  as  follows : 

To  make  a  briquette,  dust  that  is  to  be  tested  is  passed 


2 


SIDE  ELEVATION 
FIG.  37. 


FRONT  ELEVATION 

FIG.  38. 


96  HIGHWAY   ENGINEERING 

through  a  screen  with  100  meshes  to  the  linear  inch  and  is  ob- 
tained either  from  the  detritus  of  the  abrasion  test  or  by  specially 
reducing  the  stone.  The  reduction  can  be  accomplished  by 
placing  some  fragments  of  the  stone  in  one  of  the  cylinders  of  the 
abrasion  machine  together  with  one  or  more  steel  weights,  and 
allowing  the  machine  to  run  until  a  sufficient  quantity  of  the 
stone  is  pulverized.  The  dust  is  made  into  briquettes  of  circular 
section,  25  mm.  in  diameter  and  25  mm.  in  height,  by  placing  in  a 
metal  die  of  proper  dimensions,  the  dust  mixed  with  only  enough 
distilled  water  to  moisten  it  (about  4  cu.  cm.),  inserting  a  closely 
fitting  plug  on  top  of  the  wet  dust,  and  subjecting  it  to  a  pressure 
of  100  kilog.  per  sq.  cm.  The  necessary  weight  of  dust  varies 
with  the  density  and  compressibility  of  the  material,  but  gener- 
ally it  requires  about  25  gm.  of  dust  to  make  a  briquette  of 
the  above  dimensions.  Two  weeks  are  usually  allowed  for  the 
briquettes  to  dry,  at  the  ordinary  temperatures  of  a  room. 

Cuts  of  the  machine  for  testing  these  briquettes  are  shown  in 
Figs.  37  and  38.  It  consists  of  a  1-kilogram  hammer  (H) ,  arranged 
like  the  hammer  of  a  pile  driver,  on  two  vertical  guides  (D).  The 
hammer  is  raised  by  a  screw  (C),  and  dropped  automatically  from 
any  desired  height.  It  falls  on  a  plunger  (B),  which  rests  upon 
the  briquette  (0)  to  be  tested.  The  plunger  (B)  is  bolted  to 
a  crosshead  (G),  which  is  guided  by  two  vertical  rods  (F).  A 
small  lever  (J),  carrying  a  pencil  (K)  at  its  free  end,  is  connected 
to  the  side  of  the  crosshead  by  a:  link  motion,  arranged  so  that  it 
gives  a  vertical  movement  to  the  pencil  six  times  as  great  as  the 
movement  of  the  crosshead.  The  pencil  is  pressed  against  a 
drum  (A),  and  its  movement  is  recorded  on  a  slip  of  paper  fast- 
ened thereon.  The  drum  is  moved  automatically  through  a  small 
angle  at  each  stroke  of  the  hammer;  in  this  way  a  record  is  ob- 
tained of  the  movement  of  the  hammer  after  each  blow.  The 
standard  fall  of  the  hammer  for  a  test  is  1  cm.,  and  the  blow  is 
repeated  until  the  bond  of  cementation  of  the  material  is  de- 
stroyed. The  final  blow  is  easily  ascertained ;  for,  when  the  ham- 


BROKEN-STONE   ROADS 


97 


mer  falls  on  the  plunger,  if  the  material  beneath  it  can  withstand 
the  blow,  the  plunger  rebounds ;  if  not,  the  plunger  stays  at  the 
point  to  which  it  is  driven,  the  elasticity  of  the  material  being 


FIG.  39. 

completely  destroyed.     The  automatic   record   thus   obtained 
from  each  briquette  is  filed  for  future  reference.     The  number  of 

7 


98  HIGHWAY   ENGINEERING 

blows  required  to  break  the  bond  of  cementation,  as  described 
above,  is  taken  as  representing  the  binding  power  of  the  stone, 
and  is  so  used  in  comparing  this  property  in  different  road 
materials. 

Considerable  difficulty  has  been  experienced  in  keeping  the 
briquette  rigidly  in  place  under  the  plunger,  so  that  it  should  not 
be  subject  to  lateral  movements  and  complex  stresses  under  the 
blows  of  the  hammer.  The  usual  device  depended  upon  is  a  small 
brass  plate  fastened  to  the  base  of  the  machine,  with  a  bevelled 


Point  of  Failure 
82  Blows 


FIG.  40. 


hole  slightly  larger  in  diameter  than  the  briquette;  this  has 
proved  quite  unsatisfactory,  for  the  induced  side  thrusts  fre- 
quently cause  the  lower  edge  of  the  briquette  to  crumble  away 
under  the  successive  blows,  and  failure  of  the  test  specimen  to 
take  place  under  too  small  a  number  of  blows. 

In  the  laboratory  of  the  U.  S.  Department  of  Agriculture 
various  clamping  devices  were  tried  and  rejected.  Finally  the 
method  was  adopted  of  securing  the  briquette  to  the  bed  plate  by 
means  of  shellac. 

In  preparing  the  stone  dust  for  the  cementation  test,  an  auto- 
matic screen,  about  100  cm.  long  by  10  cm.  in  diameter  is  used. 
It  consists  of  a  cylinder  mounted  on  bearings  at  a  slight  angle 
with  the  horizontal,  made  of  brass  wire  netting  of  2  different 
meshes,  16  and  100  per  linear  inch,  respectively.  Into  the  upper 
end  of  the  rotating  cylinder  the  unscreened  dust  is  automatically 
fed  from  a  hopper,  and  in  its  passage  is  sifted  into  the  2  sizes. 
The  upper  end  of  the  cylinder  rests  on  wheel  bearings,  and  on  the 
bearing  surface  are  several  ridges  which  lift  the  cylinder  whenever 
they  pass  over  the  wheels.  This  shaking  device  was  introduced 
with  the  view  of  preventing  the  finer  meshes  of  the  screen  from 


BROKEN-STONE   ROADS  99 

clogging.  As  the  apparatus  is  completely  covered,  no  dust  can 
escape  into  the  air. 

The  making  of  the  briquettes  requires  considerable  skill  and 
watchfulness,  if  the  results  of  the  test  are  to  mean  anything.  The 
amount  of  water  to  be  applied  varies  with  the  nature  of  the 
material,  and  can  be  determined  only  by  trial.  The  object 
sought  is  to  have  the  wet  dust  of  the  various  specimens  of  the 
same  consistency.  With  the  small  quantities  of  dust  used  for 
each  briquette,  a  few  drops  more  or  less  will  vary  the  consistency 
quite  noticeably,  and  with  it,  the  degree  of  compacting  of  the 
mixture  under  the  lever  compression  machine,  which  will  in- 
evitably appear  in  the  variation  of  the  results  of  the  cementation 
test. 

When  the  fine  abraded  material  of  a  given  specimen  is  sifted, 
the  finest  particles  pass  through  first,  and  what  subsequently 
passes  is  coarser  and  coarser,  until  only  a  few  particles  of  the 
"  size  of  separation  "  of  the  sieve  will  pass.  Unless  the  dust 
which  has  passed  through  the  sieve  is  thoroughly  mixed,  the 
briquettes  will  give  discordant  results  on  a  test,  the  finer  material, 
in  general,  exhibiting  greater  binding  power. 

A  ball  mill  (Fig.  41)  has  been  adopted  as  the  standard  for  pre- 
paring the  dust  in  a  uniform  manner.  It  consists  of  a  flat,  circu- 
lar, cast-iron  chamber  containing  2  chilled-steel  balls,  weighing 
25  Ibs.  each,  and  of  slightly  smaller  radius  than  that  of  the  rim  of 
the  chamber.  One  kilogram  of  rock  fragments  which  will  pass 
through  a  6  mm.  opening,  but  not  through  a  1  mm.  opening,  is 
put  in  the  chamber  and  rotated  for  2J  hours,  making  5,000 
revolutions.  The  ground  material  is  then  passed  through  a 
sieve  made  of  No.  7  silk  bolting  cloth,  with  3  meshes  to  the  milli- 
metre, and  the  briquettes  are  moulded  from  the  dust  passing 
through. 

In  moulding  briquettes  for  the  cementation  test,  the  Washing- 
ton laboratory  has  modified  the  usual  procedure.  The  fine  dust 
is  mixed  with  water  and  kneaded  to  the  consistency  of  a  stiff 


100  HIGHWAY   ENGINEERING 

dough,  which  is  kept  in  a  closed  jar  for  24  hours.  It  is  then  made 
up  in  the  usual  way  into  briquettes,  which  are  allowed  to  dry  for 
12  hours  in  the  air,  and  are  then  placed  in  a  steam  bath,  where 
they  remain  for  12  hours.  After  cooling  in  a  desiccator  they  are 
tested  in  the  customary  manner.  This  modification  was  sug- 
gested by  the  results  of  certain  experiments  which  showed  that 


FIG.  41.— Ball  Mill. 

the  cementing  value  increases  progressively  if  the  dough  made 
from  the  rock  dust  is  allowed  to  stand  for  some  time  before  being 
moulded;  and  the  increase  is  greater  if  the  dough  had  been 
previously  well  kneaded. 

Tests  of  many  varieties  of  rock  dust  show  that  the  more  finely 
they  are  pulverized  the  higher  will  be  their  cementing  value 
when  moulded  under  pressure,  either  with  or  without  moisture; 
and  the  greater  the  pressure  the  higher  the  value.  Of  two  sets  of 


BROKEN-STONE   ROADS  101 

briquettes  made  with  the  same  rock  dust,  one  moulded  wet,  the 
other  dry,  the  former  invariably  yielded  the  higher  result ;  and, 
within  certain  limits,  the  more  wet  the  material  the  higher  the 
cementing  value.  That  this  is  not  due  to  a  chemical  change  in- 
duced by  the  action  of  water  has  been  shown  by  testing  briquettes 
made  of  pulverized  glass  mixed  with  alcohol,  which  yielded  like 
results.  It  was  formerly  thought  that  the  water  added  to  a  rock 
dust  acted  merely  as  a  lubricant  to  the  fine  particles,  allowing 
them  to  slide  over  each  other  more  easily  under  pressure,  and 
thus  mechanically  interlock. 

Until  quite  recently  the  cementation  values  have  been  ob- 
tained by  the  method  first  described  here,  and  most  of  the 
published  reports  of  such  tests  must  be  read  with  this  under- 
standing. 

The  cementation  test  as  practised  at  present  is  not  entirely 
satisfactory,  although  the  modifications  introduced  in  the  Wash- 
ington laboratory  constitute  a  notable  advance.  It  is  difficult  to 
obtain  uniform  and  comparable  results ;  and,  further,  it  would  ap- 
pear desirable  that  the  character  of  the  test  specimen  should 
approximate,  as  nearly  as  may  be  practicable,  the  condition  of  the 
material  on  the  roadway.  This  may  be  approached  by  making 
the  briquettes  of  a  mixture  of  the  fine  dust,  obtained  as  usual, 
and  a  definite  quantity  of  some  aggregate,  preferably  coarser 
particles  of  the  same  sample,  sifted  to  some  standard  degree  of 
fineness.  The  best  proportional  quantities,  and  the  best  size  of 
aggregate  to  be  used,  can  be  determined  only  after  numerous 
comparative  experiments.  The  size  of  the  test  specimen  might 
well  be  made  larger,  to  reduce  the  influence  on- the  result  of  small 
accidental  defects  in  the  piece.  It  is  entirely  analogous  to  the 
testing  of  briquettes  of  hydraulic  cement  made  neat,  or  with  the 
proper  admixture  of  a  standard  sand,  the  latter  giving  the  more 
valuable  and  practical  information. 

Furthermore,  since  the  surface  of  a  broken-stone  road  is  being 
constantly  abraded,  dried,  moistened,  and  recemented,  it  would 


102  HIGHWAY  ENGINEERING 

seem  to  be  desirable  to  also  determine  the  recementing  properties 
of  the  specimens,  thus  furnishing  additional  information  of 
special  practical  significance.  Formerly  this  was  done  in  the 
following  manner :  a  set  of  briquettes  of  constant  weight,  instead  of 
constant  height,  was  made  and  tested,  and  the  broken-down 
material  was  made  into  a  new  set  of  briquettes,  and  again  tested 
to  failure.  The  number  of  blows  in  the  second  case  gave  the 
value  of  the  recementing  power  of  the  fine  dust. 

Toughness  Test.  This  test  is  made  on  25  mm.  by  25  mm. 
rock  cylinders,  with  the  impact  machine  used  for  testing  the 
briquettes  of  rock  dust.  Instead,  however,  of  a  flat-end  plunger 
resting  on  the  test  piece,  as  in  the  cementation  test,  a  plunger  with 
the  lower-end  bearing  surface  of  spherical  shape,  having  a  radius 
of  1  cm.,  is  used.  It  can  be  seen  that  the  blow  as  delivered 
through  a  spherical-end  plunger  approximates  as  nearly  as  practi- 
cable the  blows  of  traffic,  and  it  has  the  further  advantage  of  not 
requiring  great  exactness  in  getting  the  two  bearing  surfaces  of 
the  test  piece  parallel,  as  the  entire  load  is  applied  at  one  point  on 
the  upper  surface.  The  test  piece  is  adjusted  so  that  the  centre 
of  its  upper  surface  is  tangent  to  the  spherical  end  of  the  plunger, 
which  is  pressed  firmly  upon  the  piece  by  two  spiral  springs  sur- 
rounding the  plunger  guide  rods.  The  cylinder  is  held  to  the 
base  of  the  machine  by  a  device  which  prevents  its  rebounding 
when  a  blow  is  struck  by  the  hammer,  which  weighs  2  kilos. 
The  test  consists  of  a  1  crn.  fall  of  the  hammer  for  the  first  blow, 
and  an  increased  fall  of  1  cm.  for  each  succeeding  blow  until  fail- 
ure occurs,  the  number  of  blows  required  to  cause  failure  being 
taken  to  represent  the  toughness.  The  cylindrical  test  pieces 
may  be  made  with  a  core  saw  designed  for  the  purpose. 

Resistance  to  Crashing.  The  ultimate  compressive  resistances 
of  cubes  of  the  material  is  determined  in  the  usual  man- 
ner by  subjecting  them  to  pressures,  and  is  expressed,  generally, 
in  pounds  per  square  inch.  Briefly  described,  the  crushing  test 
is  performed  by  placing  a  cubical  specimen  of  the  material  to 


BROKEN-STONE   ROADS 


103 


be  tested  on  the  steel  platform  of  the  testing  machine,  and  me- 
chanically applying  pressure  by  means  of  a  cross-head  which  is 
made  to  approach  the  test  piece  from  above.  The  total  pressure 
applied  is  determined  by  noting  the  number  of  pounds  recorded 


TABLE   SHOWING   THE   QUALITIES   OF   SOME   ROAD   STONE 


Locality  of  Quarry. 

Name  of  Rock. 

Wear. 

Cementation 
Value. 

Where  Used. 

Coeffi- 
cient. 

Per 
cent 

Albany  County,  N.  Y. 
Quarries   i  mile   north  from 
Dunsbach     Ferry     station 
on    N.Y.C.&  H.R.R.R.    on 

Hudson  river 
sandstone  

Chemung  grit  

Sandstone  

Calcareous  sand- 
stone 

6.78 
5.82 

6.80 
7.07 
6.87 
10.94 

5.96 

6.88 

5.88 
5.65 
5.82 
3.66 

50 
24 

26 
30 
It 
25 

Used  for  top  and 
base  of  section  2 
of  Loudon  road. 
\  No.  119,  from  Al- 
1  bany  to  Cohoes, 
I  built  during  1903 
(  by  the  State. 

Used  during  1901 
for     base    of    3£ 
miles  of  the 
Southport  r  o  ad 
to    the    south 
boundary  of  New 
York  State,  built 
I  by  State. 

Used  during  1902 
for    base    top    2 
miles  of  Norwich 
and       Plymouth 
road     No.     112, 
I  built  by  State. 

f  Used  during  1902 
for  base  of  1  mile 
of  road  south 
from      Cortland. 
Blodgett's    Mills 
road,     No.     Ill, 
built  by  State. 

Usedduringl90I 
for  base  and  top 
and    filler   of    Ja 
mile    of    Platts- 
burgh    and 
Keeseville    road, 
(  built  by  State. 

Used  during  1901 
for  base  and  top 
and    filler  of    2* 
miles   of    Platts- 
burgh and  Keese- 
ville   road,    built 
by  State. 

s.  side  of  Mohawk  river.  .    . 

Chemung  County,  N.  Y. 
Wells  Quarry,  3  miles  west  of 
Elrnira,  N.  Y  

Chenango  County,  N.  Y. 
From    ledge   5    miles   north 
of   Norwich,    on   farm   of 
Loren  Cushman,  300  feet 
west  of  Norwich  and  Plym- 
outh road  No.  112  

Cortland  County,  N.  Y. 
From  ledge  on  farm  of  O.  G. 
Kellogg,  2^  miles  s.e.  from 
Cortland,  N.  Y  

Clinton  County,  N.  Y. 
plattsburgh,   Clinton  ] 
county,    N.    Y.,    Moore's  1 
Quarry,  north  side  of  vil-  [ 
lace 

Clinton  blue  lime- 

Five  miles  south  of  Platts-  ] 
burgh,  N.  Y.,  quarry  on  1 
north    bank     of    Salmon  [ 
river  J 

Clinton  gray  lime- 
stone 

104  HIGHWAY  ENGINEERING 

by  the  balanced  scale  beam  at  the  time  of  failure.  This  value, 
divided  by  the  area  of  the  section  over  which  the  pressure  is  dis- 
tributed, gives  the  required  quantity,  i.e.,  pounds  per  square 
inch. 

The  Absorption  Test  as  made  by  the  Massachusetts  State 
Highway  Commission  consists  in  taking  a  smooth  specimen  that 
has  been  subjected  to  the  impact  and  abrasion  test,  and  which 
weighs  about  40  gms.  and  weighing  it  in  air.  It  is  then  immersed 
in  water,  where  it  is  immediately  weighed,  and  allowed  to  remain 
for  ninety-six  hours,  at  the  end  of  which  period  it  is  again  weighed 
in  the  water  as  it  is  supposed  to  have  become  completely  satu- 
rated. From  the  recorded  weights  the  absorption  is  computed 
by  the  following  formula. 

Pounds  of  water  absorbed  per  cubic  foot  of  stone  = 

x  62-5 


Here  A  =  weight  in  air, 

B  =    "      directly  after  immersion, 
C  =    "      after  ninety-six  hours. 

The  specific  gravity  and  weight  per  cubic  feet  would  be  obtained 
in  the  customary  way.  If  a  petrographic  examination  is  re- 
quired to  classify  the  rock,  a  thin  section  of  the  specimen  is 
taken  and  studied  under  the  microscope. 

The  rocks  most  commonly  used,  most  nearly  satisfying 
the  requirements  of  the  above  tests,  and  which,  from  actual  ser- 
vice, have  been  shown  to  be  best  suited  for  road-building  pur- 
poses, are  trap,  granite,  limestone,  sandstone,  fieldstone,  and 
shale,  in  the  order  of  their  importance. 

It  should  be  remembered,  however,  that  in  making  a  selec- 
tion, traffic  and  cost  should  be  studied,  and  cost  of  maintenance 
and  construction  taken  into  account. 

TRAP  is  a  hard  and  tough  igneous  rock,  very  fine-grained  and 
eminently  suited  to  road-building  purposes.  It  wears  well,  and 
yet  yields  enough  dust  to  make  up  for  that  which  has  been  car- 


BROKEN-STONE   ROADS  105 

ried  away  by  wind,  rain,  or  other  causes.  This  dust  in  itself 
possesses  superior  cementing  qualities,  so  that  the  individual 
stones  are  bonded  together  as  though  with  cement. 

It  is,  perhaps,  the  best  road  stone  that  may  be  had,  but  it  is 
found  in  comparatively  few  districts,  so  that  it  is  expensive. 
Frequently  where  the  cost  is  excessive  an  inferior  or  cheaper 
local  rock  is  used  for  a  foundation  while  a  thin  layer  of  trap  ia 
placed  on  top  of  this  to  take  the  wear. 

GRANITE  is  a  massive  rock,  granular  in  texture  and  composed 
principally  of  quartz,  feldspar,  mica,  and  hornblende.  The 
presence  of  the  quartz  makes  the  rock  brittle,  the  feldspar 
is  readily  decomposed,  while  the  mica  splits  easity.  In  spite 
of  these  facts,  because  of  its  hardness  it  wears  well,  and  makes 
a  good  road  stone.  Syenite,  which  is  a  form  of  granite  with 
the  quartz  absent,  makes  the  best  surfacing  material. 

LIMESTONE  is  frequently  and  satisfactorily  used  on  roads 
where  the  traffic  is  light,  for  it  possesses  superior  binding  quali- 
ties ;  but  it  is  neither  tough  nor  hard,  so  that  it  is  easily  reduced 
to  a  powder  to  be  washed  or  blown  away.  Very  often,  how- 
ever, limestone  will  be  mixed  with  other  material  in  which  the 
binder  is  lacking,  to  produce  its  more  complete  and  rapid  con- 
solidation. 

SANDSTONE  consists  of  a  mass  of  fine  grains  of  silica  bound 
together  by  some  cementing  material,  and  depends  for  its 
strength  upon  the  nature  of  this  cement.  Because  of  its  struc- 
tural weakness  it  is  not  a  very  satisfactory  road  stone,  as  it 
readily  disintegrates,  leaving  a  mass  of  loose  sand  grains. 

FIELD  STONE,  or  crushed  gravel,  is  often  used  on  gravel  or 
broken-stone  roads,  either  alone  or  mixed  with  some  other 
material,  and  is  eminently  suited  to  the  purpose  provided  the 
stone  is  undecomposed  and  uniform  in  character.  Lack  of  uni- 
formity will,  however,  produce  an  uneven  surface  after  a  little 
wear. 

SHALE,  which  is  an  indurated  clay,  is  of  two  kinds :  theargilla- 


106 


HIGHWAY   ENGINEEEING 


ceous  or  clayey  shale,  and  the  arenaceous  or  sandy  shale.  The 
former  is  without  value,  while  the  latter  is  extensively  used, 
particularly  as  a  top  dressing  for  stone  roads. 

FORMS  OF  CONSTRUCTION.  There  are  two  general  forms  of 
construction,  surface  and  trench.  The  former  name  is  applied  to 
that  in  which  the  stone  is  distributed  in  a  layer  over  the  surface, 


FIG.  42. — Excavating  and  Preparing  Roadbed  for  Macadam  Surface. 

Construction. 


Trench 


and  where  consolidation  usually  occurs  by  means  of  the  traffic. 
It  is  not  a  particularly  good  way  to  build  broken-stone  roads; 
but,  on  the  other  hand,  the  results  are  not  particularly  bad  if  due 
care  is  exercised,  and  it  is  cheap. 

With  the  other  form,  a  trench  of  proper  dimensions  is  dug 
along  the  line  of  highway  and,  after  proper  grading,  rolling,  and 
other  preparation,  the  broken  stone  is  placed  in  this.  The 
advantage  of  the  latter  type  is  that  the  shoulders  keep  the  stone 
in  place,  thus  preventing  spreading.  Trench  construction  is  used 
for  both  macadam  and  telford  pavements. 


BROKEN-STONE    ROADS 


107 


The  transverse  profile  of  the  subgrade  may  be  either  flat  or 
have  the  same  crown  as  that  of  the  final  surface.  In  the  former 
case  the  greater  amount  of  material  is  where  the  most  traffic 
comes,  i.e.,  in  the  centre  of  the  road,  which  is  claimed  to  be  an 
advantage  as  it  distributes  the  pressure  better.  The  more  gen- 
eral practice,  however,  favors  a  subgrade  parallel  to  the  surface 
and,  of  course,  requires  less  material. 


FIG.  43. — Macadam  Pavement  Supported  at  Sides  by  Shoulders  of  Earth, 
Trench  Construction. 

In  preparing  the  subgrade  it  is  better  to  use  a  steam  roller 
of  10  to  15  tons,  with  a  pressure  of  500  Ibs.  per  lineal  inch  of  tire, 
than  either  a  hand  or  horse  roller,  as  it  is  quicker,  heavier,  less 
expensive,  and  secures  a  more  perfect  consolidation. 

Wherever  necessary,  subsurface  drainage  should  be  installed 
as  no  amount  of  rolling  will  make  a  satisfactory  foundation  where 
the  soil  is  wet  or  in  a  position  to  become  so. 


FIG.  44. — Telford  with  Macadam  Surface,  Trench  Construction. 

THICKNESS  OF  STONE  COVERING.  Upon  the  prepared  sub- 
grade  is  spread  the  broken  stone  in  layers  and  to  a  depth  depend- 
ing upon  "  the  soil,  the  nature  of  the  stone  used,  method  of  repairs, 
and  the  amount  of  traffic  which  the  road  is  expected  to  have. 
It  should  be  so  thick  that  the  greatest  load  will  not  affect  the 
foundation.  The  weight  usually  comes  upon  a  very  small 
part  of  the  surface,  but  is  spread  over  a  large  area,  and  the  thicker 


108  HIGHWAY   ENGINEERING 

the  crust  the  more  uniformly  will  the  load  be  distributed  over 
the  foundation." 

Where  the  traffic  is  heavy,  naturally  a  thicker  surfacing  is 
required  than  where  it  is  light;  if  the  stone  is  easily  crushed  or 
broken,  it  is  easily  blown  or  washed  away,  and  more  metalling  is 
needed  than  if  it  is  hard  and  tough  and  capable  of  withstanding 
the  effect  of  traffic ;  if  the  repairs  are  periodic,  larger  quantities 


FIG.  45. — Cross-Section  of  Macadam  Road  Showing  Results  when  Loose  Stone 
is  Placed  on  Wet  Earth  Foundation. 


of  stone  must  be  applied  at  first  in  order  to  provide  for  wear  be- 
tween periods  of  repair. 

The  Massachusetts  Highway  Commission  "  has  estimated  that 
non-porous  soils,  drained  of  water,  at  their  worst  will  support 
a  load  of  about  four  pounds  per  square  inch ;  and,  having  in  mind 
these  figures,  the  thickness  of  the  broken  stone  has  been  adjusted 
to  the  traffic.  On  a  road  built  of  fragments  of  broken  stone  the 
downward  pressure  takes  a  line  at  an  angle  of  forty-five  degrees 
from  the  horizontal,  and  is  distributed  over  an  area  equal  to  the 
square  of  twice  the  depth  of  the  broken  stone.  If  a  division  of 
the  load,  in  pounds,  at  any  one  point,  by  the  square  of  twice  the 
depth  of  the  stone  gives  a  quotient  of  four  or  less,  then  will  the 
road  foundation  be  safe  at  all  seasons  of  the  year.  On  sand  or 
gravel  the  pressure  may  safely  be  placed  at  twenty  pounds  per 
square  inch." 


BROKEN-STONE   ROADS  109 

The  above  may  be  written 


where 

t  =  thickness  of  stone  in  inches  ; 

w  =  weight  of  load  in  pounds  per  square  inch  per  wheel  ; 

p  =  supporting  power  of  soil  per  square  inch. 
"  Acting  on  this  theory,  the  thickness  of  stone  on  the  Massa- 
chusetts State  roads  varies  from  4  to  16  ins.,  the  lesser  value 
being  used  on  good  gravel  or  sand,  and  the  larger  on  heavy  clay. 
In  cases  where  the  surfacing  exceeds  6  ins.  in  depth,  the  excess 
may  be  broken  stone,  stony  gravel,  or  ledge  stone,  the  material 
used  depending  entirely  upon  the  cost,  either  being  equally 
effective." 

Macadam  used  a  thickness  of  ten  inches  in  the  roads  he  built, 
but  the  depth  must  necessarily  vary  with  different  conditions. 

In  New  Jersey  the  following  thicknesses,  depending  on  grade, 
have  been  used  : 

Grade  flatter  than  1  per  cent  ........................    10  ins. 

Grade  between  1  per  cent  and  4  per  cent  .............     8  ins. 

Grade  over  4  per  cent  ..............................      6  ins. 

In  general,  however,  it  may  be  stated  that  the  thickness 
varies  between  4  and  12  ins.  for  macadam,  with  an  average 
of  6  ins.,  and  between  8  and  12  ins.  for  telford,  with  an  average 
of  8  ins. 

In  Bridgeport,  Conn.,  a  thickness  of  4  ins.  has  been  used 
satisfactorily  with  loads  averaging  6,000  Ibs.,  but  it  is  needless  to 
say  such  roads  must  conform  to  the  highest  standards  of  con- 
struction and  be  maintained  by  a  system  of  continuous  repairs. 

SIZE.  "  The  size  to  which  stone  should  be  broken  depends 
upon  the  quality  of  the  stone,  the  amount  of  traffic  to  which  the 
road  will  be  subjected,  and  to  some  extent  upon  the  manner  in 
which  the  stone  is  put  in  place.  If  a  hard,  tough  stone  is  em- 


110  HIGHWAY   ENGINEERING 

ployed,  it  may  be  broken  into  rough  cubes  or  pieces  of  about  one 
and  one-half  inches  in  largest  face  dimensions,  and  when  broken 
to  such  a  size  the  product  of  the  crusher  may  generally  be  used 
to  good  advantage  without  the  trouble  of  screening,  since  dust 
"  tailings  "  and  fine  stuff  do  not  accumulate  in  large  quantities 
in  the  breaking  of  the  tougher  stone. 

"  If  only  moderate  traffic  is  to  be  provided  for,  the  harder 
limestones  may  be  broken  so  the  pieces  will  pass  through  a 
2  in.  ring,  though  sizes  running  from  2f  to  2J  ins.  will  insure  a 
more  durable  roadway,  and  if  a  steam  roller  be  used  in  com- 
pacting the  metal  it  will  be  brought  to  a  smooth  surface  without 
much  trouble.  As  a  rule,  it  may  be  said  to  adhere  closely  to  a 
size  running  from  2J  to  2J  ins.  in  largest  face  dimensions,  and 
to  use  care  in  excluding  too  large  a  proportion  of  small  stuff  as 
well  as  all  pieces  of  excessive  size  will  insure  a  satisfactory  and 
durable  macadam  road."  Where  the  traffic  is  light  a  top  course 
of  stone  |  to  1  in.  in  size  is  employed,  while  for  heavier  loads 
1  to  2  ins.  is  used. 

Usually  it  is  recommended  to  have  the  stone  uniform  in  size, 
but  in  Massachusetts  it  is  separated  into  three  sizes  of  \  in.,  1}  in., 
and  2J  ins.  by  passing  through  screens.  The  larger  size  is  placed 
on  the  bottom  with  the  smaller  sizer  in  successive  layers  on  top. 
The  subgrade  and  each  course  is  rolled  separately,  and  the  top 
course  watered  before  rolling. 

LAYING.  In  laying  the  stone  it  is  probably  better  to  strew  it 
over  the  surface  with  a  shovel  than  to  dump  it  in  heaps  from 
carts  and  spread  it  later  with  forks  and  rakes.  The  former 
secures  a  more  even  distribution  of  the  material,  both  as  to  size 
and  quality,  though  it  costs  more. 

The  layers  should  be  about  four  to  five  inches  thick,  depend- 
ing upon  the  final  thickness  of  the  road,  and  rolling  should  be 
continued  until  each  course  is  thoroughly  consolidated.  Under 
ordinary  circumstances  this  will  result  when  the  course  has  been 
reduced  from  twenty  to  thirty  per  cent,  but  the  standard  of 


BROKEN-STONE   ROADS 


111 


judgment  should  be  not  the  percentage  of  reduction,  but  the 
firmness  of  the  pavement. 

ROLLING.  The  amount  of  rolling  depends  upon  several 
factors,  such  as  weight  of  roller,  size  and  hardness  of  stone, 
amount  of  binder  and  water  used,  nature  of  binder,  etc.  Where 


FIG.  46. — First  Course  of  Stone  on  a  Macadam  Road  as  it  Appears  when 

Ready  for  Rolling. 

the  binder  is  freely  used  together  with  an  abundance  of  water, 
consolidation  results  more  quickly  than  otherwise,  but  it  is  not 
as  satisfactory  as  if  less  binder  and  more  water  were  used  with 
more  rolling. 

Hard  stone  requires  more  rolling  than  soft. 


FIG.  47. — First  Course  of  Stone  Partially  Rolled,  Showing  how  the  Roller 

Packs  it. 


In  all  cases  rolling  should  proceed  from  the  sides  toward  the 
centre  so  as  to  preclude  the  possibility  of  the  stone  thinning  out 
at  the  edges,  and  the  rolling  at  the  sides  should  be  completed 
before  the  roller  proceeds  toward  the  centre.  Wetting  the  stone 


112  HIGHWAY  ENGINEERING 

during  this  process  hastens  the  consolidation,  "  decreases  crush- 
ing under  the  roller,  and  assists  the  filling  of  the  voids  with  the 
binder." 

THE  BINDER  may  be  screenings  of  trap,  limestone,  sandstone, 
shale,  clay,  or  loam.  It  is  applied  to  each  successive  layer,  and 
liberally  sprinkled  with  water  for  the  purpose  of  producing  the 
more  complete  consolidation  of  each  course. 

WIDTH.  In  Massachusetts  the  standard  width  of  metalling  is 
fifteen  feet  with  shoulders  of  three  feet  at  each  side  shaped  to  the 
same  cross-section.  Where  the  traffic  is  excessive  these  shoulders 
are  covered  with  gravel,  but  otherwise  the  natural  soil  is  used. 
Ten  and  twelve  feet  have  been  used,  but  the  former  has  been 


FIG.  48. — First  Course  Thoroughly  Rolled.     Small  Stones,  Gravel,  Dirt,  or 
Sand,  if  Present,  Prevent  Such  a  Complete  Consolidation. 

found  to  be  uneconomical  except  under  very  light  traffic.  In 
New  Jersey,  the  width  varies  between  9  and  16  ft.,  though  the 
more  common  width  is  10  to  12  ft. 

The  width  of  a  stone  road  depends  upon  the  amount  of 
traffic,  and  is  an  important  question  to  decide,  as  the  stone  is  ex- 
pensive. Frequently  to  save  expense  the  central  portion  will  be 
paved  with  the  telford  or  macadam  where  the  most  travel 
comes,  and  wings  will  be  employed  at  the  sides  to  take  the  lighter 
traffic  and  to  permit  of  turning  out.  These  wings  are  part  of  the 
stone  pavement,  but  of  a  less  thickness,  and  without  the  founda- 
tion of  cobble  where  telford  is  used.  Beyond  these  wings  there 
may  be  shoulders,  or,  if  the  wings  are  notspresent,  the  shoulders 


BROKEN-STONE   ROADS  113 

are  placed  next  the  pavement,  serving  the  purpose  not  only  of 
holding  the  stone  in  place,  but  providing  room  for  turning  out  as 
well. 

CROSS-SECTION.  The  form  of  the  profile  may  be  either  the 
intersection  of  two  planes  at  the  centre  of  the  roadway  or  a 
curve  in  the  form  of  a  circle,  ellipse,  or  parabola. 

In  the  former  case  the  ordinates  are  proportional  to  the 
distance  from  the  centre;  in  the  latter,  or  where  the  parabolic 
curve  is  employed,  the  ordinates  are  proportional  to  the  square 
of  the  distance  from  the  centre.  The  following  rule  may  also  be 
used :  "  Divide  the  roadway  into  3  equal  parts,  and  starting  from 
the  centre  give  a  fall  of  .03  ft.  per  ft.  for  the  1st  part,  .04  ft.  per  ft. 
for  the  2d,  and  .05  ft.  per  ft.  for  the  3d.  If  the  roadway  is  very 
wide,  divide  the  |  roadway  into  4  parts,  giving  a  fall  of  .02,  .03, 
04,  and  .05  ft.  per  ft.  to  the  respective  sections.  If  the  roadway 
is  narrow,  divide  the  J  into  2  parts,  and  give  falls  of  .04  and  .05 
ft.  per  ft.  to  the  2  sections  respectively." 

CROWN.  The  amount  of  crown  will  vary  between  a  slope  of 
1  in  12  and  a  slope  of  1  in  40,  depending  upon  the  method  of 
making  repairs,  the  longitudinal  grade,  and  the  width  of  roadway 
Where  the  roadway  is  very  wide,  a  smaller  crown  should  be 
given  to  avoid  an  excessive  rise  at  the  centre  with  the  consequent 
high  velocities  of  surface  waters.  If  at  the  same  time  the  re- 
pairs are  made  continuously,  a  minimum  crown  will  satisfactorily 
care  for  the  water  falling  on  the  pavement.  This,  however, 
should  never  be  less  than  the  above  minimum  ratio.  Where  the 
road  is  narrow,  the  crown  may  be  legitimately  increased  without 
fear  of  the  surface  waters  damaging  the  roadway,  and  if  along 
with  this  the  repairs  are  made  periodically,  the  maximum  may 
be  reached.  Where  repairs  are  periodic  a  greater  thickness  of 
metalling  is  given  at  the  centre,  to  allow  for  the  wear  during  the 
intervals  between  which  repairs  are  made. 

The  effect  of  grade  upon  crown  is  shown  in  the  following  table 
from  the  Rhode  Island  Report: 
8 


114  HIGHWAY   ENGINEERING 

Longitudinal  Slope.  Transverse  Slope. 

£  to  4  per  cent 1  in  25 

4  to  6  per  cent 1  in  20 

6  to  9  per  cent 1  in  12£ 

Repairs  and  Maintenance.  "  Repairs  of  stone  roads  should 
begin  the  day  they  are  opened  to  traffic,  as  the  attention  they 
receive  the  first  few  months  of  use  determines  their  usefulness 
and  length  of  life." 

Long  experience  having  proven  that  the  best  results  are  ob- 
tained at  a  less  cost  by  a  system  of  continuous  small  repairs,  the 
Massachusetts  Highway  Commission  has  adopted  this  method 
of  maintaining  that  State's  highways.  The  cost  is  equally 
divided  between  the  roadway  proper  and  the  sides. 

The  durability  of  roads  depends  wholly  upon  the  power  of  the 
materials  of  which  they  are  composed  to  resist  those  natural  and 
artificial  forces  which  are  constantly  acting  to  destro}^  them. 
The  fragments  of  which  they  are  constructed  are  liable  to  be 
attacked  in  cold  climates  by  frost,  and  in  all  climates  by  water 
and  wind.  If  composed  of  stone  or  gravel,  the  particles  are  con- 
stantly grinding  against  each  other  and  being  exposed  to  the 
impact  of  the  tires  of  vehicles  and  the  feet  of  animals.  At- 
mospheric agencies  are  also  at  work  decomposing  and  disinte- 
grating the  material.  It  is  obviously  necessary,  therefore,  that 
great  care  be  exercised  in  selecting  for  the  surfacing  of  roads 
those  stones  which  are  less  liable  to  be  destroyed  or  decomposed 
by  these  physical,  dynamical,  and  chemical  forces. 

The  destructive  agents  of  stone  roads  are  wind,  rain,  frost, 
horses'  hoofs,  and  wagon  wheels.  The  following  is  abstracted 
from  a  report  on  Repairs  of  Macadam  Roads  by  E.  G.  Harrison 
made  to  the  Department  of  Agriculture,  U.  S.  A. 

The  neglect  of  repairs  to  public  roads  is  very  poor  economy. 
With  the  greatest  possible  care  an  earth  roadbed  cannot  be  made 
strictly  uniform  as  to  solidity,  and  heavy  loads  passing  over  the 
crust  formed  by  the  stones  will  press  some  of  the  stones  into  soft 


BROKEN-STONE   ROADS  115 

places  in  the  earth  bed,  and  this  in  time  will  cause  a  defect  on  the 
surface  of  the  road.  A  very  slight  depression  will  at  first  appear, 
which  may  be  detected  only  after  a  rain  (by  the  water  which  will 
remain  for  some  time  in  the  depression).  If  this  depression  is 
permitted  to  remain  it  will  soon  become  deeper  and  broader. 
As  the  wagon  wheels  go  in  and  out  of  it  they  grind  out  the  stone 
softened  by  water,  and  cut  down  the  sides,  so  that  what  was  at 
first  a  slight  depression  soon  becomes  a  hole.  Such  neglect 
causes  subsequent  repair  to  be  expensive. 

CAUSES   WHICH  MAKE    REPAIRING   NECESSARY 

It  will  be  well  to  consider  some  of  the  causes  which  make  re- 
pairing necessary,  so  that  they  may  be  avoided  or  removed  as 
far  as  possible.  They  are : 

(1)  Defective  construction  of  earth  bed. 

(2)  Failure  to  cut  off  underground  water  by  drainage. 

(3)  Rain  or  storm  water  which  is  permitted  to  lie  in  pools 
along  the  roadsides  or  in  side  ditches  which  do  not  carry  the 
water  from  the  road. 

(4)  The  side  slope  being  insufficient  to  carry  the  storm  water 
from  the  road  to  the  side  ditches. 

(5)  The  longitudinal  grade  of  the  road  being  greater  than  the 
slope  from  centre  to  sides. 

(6)  The  formation  of  ruts. 

(7)  Ravelling,  or  picking  up  loose  stone. 

(8)  Surface  stone  not  of  proper  quality  and  not  uniform. 

(9)  Roadbed  not  sufficiently  compacted. 

(10)  Accumulation  of  trash  or  rubbish  on  the  road. 

These  causes  will  now  be  considered  and  remedies  suggested : 
(1)  Defective  construction  of  the  roadbed  results  in  a  sub- 
grade  which  has  not  been  thoroughly  compacted,  but  contains 
spots  of  soft  earth.  This  soft  earth  should  be  removed  and  re- 
placed by  other  earth,  so  as  to  make  the  whole  roadbed  surface  as 
uniform  as  possible.  If  this  is  not  done,  heavily  loaded  teams 


116  HIGHWAY   ENGINEERING 

passing  over  the  finished  road  will  press  the  stones  down  into  the 
soft  places,  making  depressions  in  the  surface  of  the  road  which 
will  be  filled  with  water  during  rains.  The  water  will  afterward 
percolate  through  the  stone  bed,  making  the  earth  still  softer, 
and  the  depression  will  soon  become  greater.  The  remedy  in  this 
case  must  be  applied  to  the  roadbed  itself,  for  after  the  stone 
has  been  put  in  place  defects  in  the  roadbed  cannot  be  cured. 

Wherever  a  depression  large  enough  to  hold  a  shovel  of  broken 
stone  appears  in  the  surface  of  the  finished  road  the  loose  ma- 
terial found  in  the  hole  should  be  taken  out,  the  hole  filled  with 
new  stone  broken  to  a  size  not  larger  than  one  and  one-half  inches, 
and  material  taken  from  the  hole  spread  over  the  broken-stone 
surface  for  a  binding.  It  should  then  be  compacted  by  ramming 
or  rolling  until  it  is  made  to  correspond  to  the  rest  of  the  road 
surface.  The  broken  stone  should  in  no  case  be  left  lying  loose, 
for  this  allows  the  storm  water  to  pass  through,  and  the  earth 
continues  to  soften;  moreover,  many  of  the  loose  stones  would 
be  scattered  over  the  road  surface  and  would  become  not  only 
bad  for  horses'  feet  and  damaging  to  wagons,  but  uncomfortable 
for  those  who  ride.  Loose  stone  on  a  hard  stone  surface  loosens 
the  other  stones  when  loaded  teams  pass  over  them. 

(2)  Many  roadbeds  become  soft  and  irregular,  because  the 
underground  water  was  not  cut  off  by  drains  when  the  road  was 
constructed.  This  is  one  of  the  principal  sources  of  the  many 
defects  in  roads  which  cause  depressions  and  ruts.  To  remedy 
this  defect,  tile  or  stone  drains  should  be  placed  a  short  distance 
from  the  roadbed  on  the  side  nearest  to  where  the  springs  are 
supposed  to  have  their  source.  If  it  is  uncertain  on  which  side 
of  the  road  the  springs  rise,  drains  should  be  placed  on  both  sides 
at  sufficient  depth  to  cut  off  the  underground  water.  When 
water  is  permitted  to  pass  under  the  roadbed,  as  soon  as  it  strikes 
soft  earth  or  sand  it  rises  by  capillary  attraction  to  the  surface 
and  softens  the  earth  bed.  Much  of  the  cost  of  road  repairs 
could  be  saved  by  proper  attention  to  drainage. 


BROKEN-STONE   ROADS  117 

(3)  Pools  of  water  should  never  be  allowed  to  remain  along 
the  roadside  or  in  the  ditches;  the  latter  should  always  be  kept 
open  and  clear,  so  that  all  storm  water  may  pass  to  the  nearest 
natural  waterway.     The  surface  on  the  sides  of  the  paved  road- 
way should  always  be  kept  at  proper  slope  to  carry  water  to  side 
ditches,  and  no  holes  or  obstructions  of  any  kind  allowed  to  stop 
the  free  passage  of  water  from  the  road  to  the  side  ditches. 
Water  in  pools  along  the  road  will  soften  the  earth,  and  much  of 
it  will  pass  down  until  it  comes  to  a  hard  stratum  and  will  then 
follow  the  dip  of  the  stratum,  which  may  take  it  under  the  stone 
construction,  where  it  will  act  in  the  same  way  as  water  from 
springs.     By  proper  attention  this  cause  of  repair  can  easily  be 
avoided. 

(4)  When  stone  road  surface  has  not  been  constructed  with 
sufficient  slope  or  grade  from  crown  to  side  ditches,  so  that  all  the 
storm  water  does  not  pass  off  quickly,  but  remains  in  the  slight 
depressions  and  wagon  tracks,  the  road  surface  will  become  soft 
and  will  wear  more  easily.     Dirt  which  is  carried  on  by  wagon 
wheels  will  also  remain  and  accumulate  when  there  is  not  suf- 
ficient grade  to  carry  it  off  with  rainfalls.     The  remedy  is.  to  place 
enough  stone  in  the  centre  of  the  road  to  give  it  the  required 
slope  or  grade,  which  should  never  be  less  than  one-half  inch  to 
the  foot.     Care  should  be  taken  to  keep  the  earth  surface  between 
the  metal  construction  and  the  side  ditches  of  the  same  grade,  if 
possible,  and  in  no  case  of  less  grade. 

(5)  When  the  longitudinal  grade  is  greater  than  the  slope 
from  centre  of  road  to  side  ditches,  the  water  from  rainstorms  and 
melting  snow  will  follow  the  metal  construction  with  the  run  of 
the  road,  increasing  in  quantity  and  force  according  to  the  length 
of  the  grade,  causing  washes  in  the  road  surface. 

It  is  better  to  construct  a  road  on  a  grade  not  exceeding  5  ft. 
to  the  hundred,  and  then  the  slope  can  be  made  6  or  7  per  cent. 
But  there  are  cases  where  it  is  not  practical  so  to  change  the  grade 
of  the  road  as  to  reduce  it  to  5  per  cent,  and  the  road  cannot  be 


118  HIGHWAY   ENGINEERING 

relaid  so  as  to  avoid  the  steep  grade.  In  such  cases  the  best 
possible  remedy  must  be  applied.  To  take  the  water  from  the 
metal  construction,  a  cut  or  depression  can  be  made  at  certain 
intervals,  starting  at  about  two  feet  from  the  crown  of  the  road 
and  running  diagonally  with  the  grade  to  the  side  ditches,  widen- 
ing and  deepening  as  it  gets  near  to  the  side  ditches.  It  need  not 
be  so  deep  as  to  inconvenience  the  travel,  but  deep  enough  to 
carry  off  the  storm  water.  The  greater  the  grade  the  more  cuts 
will  be  required. 

(6)  Ruts  are  generally  formed  by  the  use  of  narrow  tires  on 
wagons  carrying  heavy  loads.  They  are  more  easily  formed 
when  the  road  surface  is  soft,  but  narrow  tires  with  heavy  loads 
will  cut  out  the  stone  and  form  ruts  on  the  hardest  surface,  par- 
ticularly on  narrow  roadbeds.  A  two-inch  tire  soon  wears  away 
on  the  sides  so  as  to  become  only  one  inch  wide  on  the  bearing 
surface,  and  the  whole  weight  of  wagon  and  load  is  supported  on 
about  four  square  inches  bearing  on  the  road  surface.  When 
in  motion  it  tears  away  the  stone,  making  holes  and  forming  ruts 
when  allowed  to  run  in  the  same  tracks — a  condition  which  can- 
not well  be  avoided  on  narrow  roads.  The  ruts  deepen  and 
harden  by  use,  and  the  horses,  finding  less  resistance  to  the  wheels 
in  the  ruts,  will  walk  so  as  to  get  the  wheels  to  follow  the  ruts. 
Wide  tires  will  greatly  prevent  ruts,  but  even  wide  tires  will 
make  ruts  if  allowed  to  run  continually  in  one  track. 

In  order  to  distribute  travel  over  the  road  so  as  to  prevent 
the  formation  of  ruts,  this  plan  is  recommended : 

Have  a  double-tree  made  of  such  length  that  the  ends  will  be 
in  line  with  the  wagon  wheels.  The  single-trees  to  which  the 
traces  are  hitched  being  attached  to  the  ends  of  the  double-tree 
will  bring  the  horses  directly  in  line  with  the  wagon  wheels,  and 
the  wheels  will  follow  the  horse  and  pass  over  the  road  where  he 
steps.  As  the  horse  will  not  walk  in  a  rut  nor  go  into  a  hole  un- 
less compelled,  the  wagon  wheels  also  will  avoid  them.  If  the 
horses'  sharpened  shoes  should  loosen  any  stones,  the  wide 


BROKEN-STONE   ROADS  119 

tires  of  the  wagon  wheels  following  him  will  roll  them  into 
place  again. 

Another  plan  to  prevent  ruts,  and  at  the  same  time  to  im- 
prove the  road  by  use,  is  to  make  the  axle-trees  of  the  wagon  of 
different  lengths,  so  that  the  wheels  on  the  front  axle  will  not 
be  followed  by  those  on  the  rear  axle. 

(7)  Ravelling  or  picking  up  loose  stones  is  made  possible  by 
the  moisture  being  taken  from  the  binding  material.  The  stones 
on  the  surface  of  the  road  become  loose  and  are  easily  displaced 
both  by  the  horses'  shoes  picking  them  up  and  by  the  wheels. 
This  can  be  remedied  only  by  applying  water  to  the  road  surface, 
but,  as  it  happens  in  dry,  hot  weather,  the  water  when  applied 
soon  evaporates,  and  watering  on  country  roads  is  expensive. 
If  the  lengthened  double-trees  before  mentioned  are  used  with 
wide  tires,  the  wheels  will  pack  into  the  roadbed  as  they  pass 
over  them  the  loose  stones  picked  up  by  the  horses. 

It  is  the  light  travel,  particularly  with  one  horse,  that  causes 
much  of  the  displacement  of  surface  stones  in  dry  times,  and  there 
seems  to  be  no  way  to  avoid  it.  When  sprinkling  is  too  expen- 
sive a  light  coat  of  gravelly  sand  or  clay  gravel  may  be  applied 
with  good  effect,  as  it  will  restore  the  binding.  This  should  be 
well  rolled  to  bed  the  already  loose  stone.  Clay  earth  should 
never  be  used,  as  it  will  pick  up  the  stone  where  wet. 

Whenever  it  is  practicable,  stone  roads  should  have  an  earth 
or  gravel  roadway  on  each  side  of  the  stone  construction,  or  at 
least  on  one  side.  This  was  always  done  in  the  early  construc- 
tion of  macadam  turnpike  roads  in  Pennsylvania.  They  took 
the  name  of  "summer  roads,"  from  the  fact  that  they  were  pre- 
ferred for  light  travel  in  dry  weather  and  during  the  summer 
months.  This  saves  the  stone  road  from  much  damage  by 
ravehing.  Roads  constructed  in  this  manner  are  much  less  ex- 
pensive to  maintain,  and  it  will  be  found  that  the  extra  cost  for 
side  roads  will  be  the  most  economical  way  to  preserve  the  stone- 
road  construction. 


120  HIGHWAY   ENGINEERING 

(8)  Much  of  the  general  repair  to  stone  roads  is  due  to  the 
stone  used  for  surface  being  of  an  inferior  quality.     The  sedi- 
mentary stones  are  often  used,  such  as  limestone,  shale,  slate, 
sandstone,  mica  schist,  and  many  stratified  stones.     Some  of 
these  kinds  of  stone  will  dissolve  when  exposed  to  rain  water 
followed  by  heat,  and  some  are  disrupted  by  frost  because  they 
absorb  water.     Whenever  it  is  possible,  none  other  than  igneous 
or  volcanic  stone  should  be  used  for  surfacing.     The  sedimentary 
stone  above  mentioned  and  others  of  like  kind  can  be  used  in  the 
foundation,  but  the  surface  stone  should  be  hard  and  tough.     It 
should  wear  smooth  and  not  be  liable  to  crush.     What  is  now 
generally  known  as  trap  rock  is  to  be  preferred  when  it  can  be 
obtained. 

Limestone  is  found  generally  throughout  this  country.  The 
harder  kind  of  limestone,  that  which  contains  much  silica  or  crys- 
tallized matter,  is  the  best.  The  soft  limestone  should  not  be 
used,  as  it  soon  grinds  into  dust  or  dissolves  by  action  of  water 
and  air.  Whatever  kind  of  stone  is  used  should  be  as  far  as  pos- 
sible of  a  uniform  character.  It  is  the  hard  and  soft  stories  placed 
on  the  surface  together  that  cause  roughness  and  holes. 

(9)  The  material  for  the  road  may  all  be  of  the  proper  kind, 
but  if  this  material  is  not  put  together  properly  the  road  will  be 
expensive  to  maintain.     The  material  should  be  put  on  in  layers 
and  thoroughly  compacted  by  repeated  rolling  of  each  course, 
so  that  when  finished  it  will  be  impervious  to  water. 

A  stone  road  properly  constructed  will  not  soften  after  rains 
or  be  disturbed  by  freezing.  The  water  will  be  cast  off  at  right 
angles  to  the  centre  of  the  road  to  the  side  ditches,  and  the  road 
surface  will  only  need  repairing  where  the  stone  wears  away 
legitimately  under  the  wheels  of  the  wagons  and  the  horses' 
feet.  Maintenance  solely  from  these  causes  will  not  be  found 
costly. 

(10)  The  road  surface  should  be  kept  cleaji.     A  road  surface 
dirty  from  wear  and  from  dirt  brought  on  by  wheels  from  clay 


BROKEN-STONE   ROADS  121 

roads  or  from  leaves  or  trash  of  any  kind,  which  are  allowed  to 
remain  on  the  surface,  soon  begins  to  wear  and  to  be  in  need  of 
repair.  The  dust  from  wear  is  often  blown  off,  but  may  be  found 
in  considerable  quantities  in  sheltered  places.  If  allowed  to 
remain,  rain  turns  it  into  mud,  and  the  stone  bed  will  be  softened 
and  ruts  and  ditches  formed.  It  will  be  found  economical  to 
have  all  surplus  dirt  removed.  It  does  not  cost  much  if  attended 
to  promptly.  The  dry  dust  can  be  removed  by  sweeping,  and 
the  dirt  and  mud  by  scraping  with  hoes.  Such  material  is  so 
mixed  with  droppings  of  horses  that  it  contains  considerable 
fertilizing  matter  and  can  frequently  be  sold  for  enough  to 
pay  for  sweeping,  scraping,  and  removal.  A  clean  road  is  not 
only  important,  economically  considered,  but  it  adds  greatly  to 
the  comfort  of  those  who  use  the  road.  Roads  are  constructed 
and  maintained  for  the  comfort  as  well  as  the  pecuniary  benefit 
of  those  who  use  them. 

Wind  tends  to  remove  the  dust  from  the  surface,  and  from 
between  the  stones,  which,  if  left  there  in  not  too  excessive 
amounts,  protects  the  stone  from  traffic  and  does  not  inconveni- 
ence travellers. 

Rain  in  excess  removes  the  binder  or  softens  it,  so  that  it 
loses  its  function  of  bonding  the  stones  together. 

Frost  heaves  the  road,  causes  cracks,  and  produces  mud 
when  leaving  the  ground. 

Horses'  hoofs  and  wagon  wheels  both  abrade  and  break  the 
stone.  This  action  is  very  much  more  pronounced  where  the 
binder  permits  the  stones  to  move,  as  they  then  roll  one  upon 
the  other,  causing  wear,  or  become  loose  and  are  crushed  on  the 
surface.  To  resist  this  a  hard  and  tough  stone  must  be  selected 
with  an  excellent  binder. 

Horses'  hoofs  tend  to  loosen  the  pavement  materially  by 
picking  up  or  displacing  the  stones,  particularly  on  steep  grades. 

One  of  the  chief  sources  of  trouble  is  " ravelling,"  i.e.,  the 
loosening  of  the  stones,  and  the  consequent  scattering  of  the 


122  HIGHWAY  ENGINEERING 

loose  fragments  over  the  surface.  On  lightly  travelled  ways 
this  ravelling  is  more  likely  to  occur  than  on  roads  with  heavy 
traffic.  Various  expedients  have  been  adopted,  but  "  the  only 
remedy  which  gives  any  degree  of  satisfaction  is  to  sprinkle  sand 
over  the  surface  as  often  as  needed.  This  coating  of  sand  is  only 
a  small  fraction  of  an  inch  in  thickness  and  spread  over  a  width 
of  about  eight  feet  in  the  centre  of  the  roadway."  Roads  that 
are  exposed  to  the  action  of  the  wind  may  require  such  treat- 
ment several  times  a  year. 

Water  is  also  sometimes  used,  or  a  surfacing  of  gravel  or 
fine  stone  may  be  applied. 

To  remedy  ruts  or  depressions,  heaps  of  stone  should  be 
kept  at  the  roadside  for  immediate  application.  Ruts,  next  to 
ravelling,  require  more  attention  than  any  other  factor  in  main- 
tenance. These  may  be  caused  by  heavy  loads,  narrow  tires, 
tracking,  etc.,  but  should  be  corrected  by  filling  in  with  new 
material,  rather  finer  than  the  original  and  containing  an  excess 
of  good  binder. 

It  is  not  considered  a  good  plan  to  coat  a  long  length  of  road 
with  material  at  once,  because,  if  this  is  done,  vehicles  avoid 
going  over  the  macadam,  and  thus  prevent  it  from  consolidating 
quickly.  If  short  lengths  only  of  the  road  are  put  under  repair, 
the  drivers  find  it  more  troublesome  to  be  constantly  avoiding 
them  than  to  keep  straight  on  their  course,  and  thus  the  material 
is  made  to  bind  much  sooner. 

After  April  and  in  summer,  or  the  dry  months  of  the  year,  all 
loose  stones  should  be  removed  from  the  road,  for,  if  allowed  to 
remain,  wheels  passing  over  them  loosen  the  material  on  which 
those  stones  rest,  and  thus  cause  much  damage  to  the  surface 
of  the  road. 

The  proper  maintenance  of  a  road  consists  in  keeping  the 
surface  always  smooth  for  traffic  and  in  taking  care  that  the 
thickness  of  the  macadam  is  not  unduly  diminished  by  wear. 
A  road  may  be  smooth  on  the  surface,  but,  if  the  material  is 


BROKEN-STONE   ROADS  123 

nearly  worn  away,  it  cannot  be  considered  to  have  been  properly 
maintained.  To  keep  a  road  in  an  efficient  manner  unceasing 
vigilance  is  required.  Ruts  and  hollows  should  be  at  once  filled 
in  with  macadam,  and  all  weak  places  as  soon  as  observed  treated 
similarly. 

A  common  fault  is  to  put  too  great  a  thickness  of  stone  down 
at  once.  Penfold  says : 

"  It  is  one  of  the  greatest  mistakes  in  roadmaking  that  can  be 
committed  to  lay  on  thick  coats  of  materials,  and  when  under- 
stood it  will  no  longer  be  resorted  to.  If  there  be  substance 
enough  already  in  the  road,  which,  indeed,  should  always  be  care- 
fully kept  up,  it  will  never  be  right  to  put  on  more  than  a  stone's 
thickness  at  a  time.  A  cubic  yard,  nicely  prepared  and  broken 
to  a  rod  superficial,  will  be  quite  enough  for  a  coat,  and  will  be 
found  to  last  as  long  as  double  the  quantity  put  on  unprepared 
and  in  thick  layers.  There  is  no  grinding  to  pieces  when  so 
applied;  the  angles  are  preserved  and  the  material  is  out  of  sight 
and  incorporated  in  a  very  little  time.  Each  stone  becomes  fixed 
directly  and  keeps  its  place,  thereby  escaping  the  wear  and  fret- 
ting which  occur  in  the  other  case." 

For  repairs  of  this  nature,  where,  in  fact,  the  mere  surface  of 
the  road  only  is  sought  to  be  put  in  order,  no  binding  material  is 
used  or  necessary.  The  wheels  of  the  carriages  gradually  push 
the  stones  into  their  places,  and  make  them  bind  with  the  old 
material  on  the  road.  Some  engineers  are  of  opinion  that  no 
macadam  should  be  laid  down,  however  thin  the  coating  may  be, 
without  the  surface  of  the  road  being  roughened  with  a  pick. 
There  is  no  doubt  that  this  tends  to  make  the  new  material  bind 
with  the  old  much  sooner,  but,  on  the  other  hand,  it  tends  to 
disturb  and  to  weaken  the  crust  if  it  should  be  very  thin. 

For  more  extensive  repairs,  i.e.,  when  a  road  has  been  allowed 
to  become  very  thin,  and  it  is  necessary  that  a  considerable  thick- 
ness of  material  should  be  laid  on,  the  road  must  be  what  Mac- 
adam termed  "  lifted/'  or  broken  with  a  pick  to  the  depth  of  two 


124  HIGHWAY   ENGINEERING 

or  three  inches,  and  all  large  stones  must  be  thrown  aside  to  be 
broken  to  the  required  dimension.  A  thin  layer  of  new  macadam 
must  now  be  added,  and  the  road  rolled.  It  will  usually  be  found 
that  no  binding  material  will  be  necessary.  When  this  layer  has 
become  consolidated,  another,  two  or  three  inches  thick,  should 
be  laid  down  and  again  rolled,  and  so  on  until  the  desired  thick- 
ness of  material  for  the  road  has  been  obtained. 

Macadam  objected  to  the  use  of  any  binding  material,  such 
as  gravel,  sand,  chalk,  etc.,  being  used  with  the  view  to  help  the 
macadam  to  bind,  but  the  almost  universal  practice  now 
is  to  sprinkle  some  such  material  over  the  macadam  before 
rolling  it. 

No  road  should  be  lifted  unless  it  has  been  softened  with  rain, 
and  there  is  plenty  of  water  to  finish  the  work  of  reformation. 
To  lift  and  remake  a  road  in  dry  summer  weather  should  not  be 
attempted.  The  work  should  be  deferred  to  the  later  months  of 
the  year,  but  not  too  late,  lest  frosts  should  set  in.  Some  engi- 
neers consider  October  the  best  month  in  the  year  for  lifting  a 
road,  so  that  the  material  may  be  sifted  and  sorted  when  dry,  and 
be  consolidated  in  November  and  December. 

"  No  addition  of  materials  is  to  be  brought  upon  a  road  un- 
less, in  any  part  of  it,  it  be  found  that  there  is  not  a  quantity  of 
clean  stone  equal  to  10  ins.  in  thickness. 

"  The  stone  already  in  the  road  is  to  be  loosened  and  broken 
up,  so  that  no  piece  shall  exceed  6  oz.  in  weight. 

"  The  road  is  then  to  be  laid  as  flat  as  possible.  A  rise  of  3 
ins.  from  the  centre  to  the  side  is  sufficient  for  a  road  30  ft. 
wide. 

"  The  stones  when  loosened  in  the  road  are  to  be  gathered 
off  by  means  of  a  strong,  heavy  rake,  with  teeth  2J  ins.  in  length, 
to  the  side  of  the  road  and  there  broken,  and  on  no  account  are 
stones  to  be  broken  on  the  road. 

"  When  the  great  stones  have  been  removed  and  none  left  in 
the  road  exceeding  6  oz.,  the  road  is  to  be  put  in  shape  and  a 


BROKEN-STONE    ROADS  125 

rake  employed  to  smooth  the  surface,  which  will  at  the  same 
time  bring  to  the  surface  the  remaining  stone  and  will  allow  the 
dirt  to  go  down. 

"  When  the  road  is  so  prepared,  the  stone  that  has  been  broken 
by  the  side  of  the  road  is  then  to  be  carefully  spread  over  on  it. 
This  is  rather  a  nice  operation,  and  the  future  quality  of  the 
road  will  greatly  depend  on  the  manner  in  which  it  is  performed. 
•The  stone  must  not  be  laid  on  in  shovelfuls,  but  scattered  over 
the  surface,  one  shovel  following  another  and  spreading  over  a 
considerable  space." 

A  little  new  macadam,  however,  mixed  with  the  old,  will  con- 
siderably improve  the  surface  of  the  road.  The  old  material 
lifted  with  a  pick,  even  if  broken  afresh,  never  has  the  sharp 
edges  of  new  macadam,  and  much  of  it  is  too  rounded  to  bind 
in  the  same  effective  manner  as  freshly  broken  stone.  More- 
over, a  great  portion  of  the  old  macadam  when  lifted  will  be 
found  to  consist  of  material  which  has  been  reduced  either  to 
dust  or  to  too  small  a  size  to  be  fit  for  subsequent  use.  This 
material  ought  to  be  rejected,  or,  if  used,  it  should  only  be  em- 
ployed for  binding  purposes. 

The  breaking  up  of  winter  is  usually  a  very  severe  period  on 
any  road,  but  it  has  been  the  experience  in  Massachusetts  that 
"  a  thorough  rolling  with  a  steam  roller  in  the  spring  after 
the  frost  has  left  the  ground,  but  before  the  subgrade  is  dry, 
is  one  of  the  best  means  of  keeping  a  stone  road  in  good 
condition." 

Patching,  which  consists  in  applying  thin  layers  of  stone  to 
depressions  that  have  been  formed  in  the  roadway,  must  of  neces- 
sity be  resorted  to  in  the  maintenance  and  repair  of  stone  roads. 
Such  applications  are  made  so  as  to  reestablish  the  road  to  its 
original  thickness,  and  hence  the  amount  of  stone  coating  should 
vary  in  depth  according  to  the  needs  of  the  road  at  different 
points.  Where  long  stretches  are  to  be  thus  treated  the  stone 
should  be  scattered  over  only  a  small  section,  or  sections  at  a 


126  HIGHWAY   ENGINEERING 

time,  so  placed  that  traffic  may  not  avoid  it,  but  pass  over  it  and 
thus  consolidate  the  material.  Such  repairs  must  always  be 
made  with  stone  rich  in  binder. 

The  following  are  the  specifications  for  stone  roads  as  used 
in  the  State  of  New  Jersey. 


STANDARD  STATE  AID  SPECIFICATIONS  FOR  STONE 

ROADS 

FOR    A    STONE    ROAD    IN COUNTY,    NEW 

JERSEY,  KNOWN  AS 

BEGINNING  AT 

EXTENDING  TO 

A   DISTANCE   OF FEET   OR MlLES 

STONE FEET  WIDE INCHES  DEEP 

EARTH FEET  WIDE.     TOTAL  WIDTH FEET 

WORK  TO  BE  PERFORMED 

1.  The  work  to  be  performed  will  consist  in  furnishing  all 
material,  tools,  machinery,  and  labor  necessary  for  the  efficient 
and  proper  grading  of  roadway,  side  ditches,  and  side  banks, 
laying,  spreading,  and  rolling  of  road  metal,  and  leaving  the  road- 
way complete  in  every  manner  ready  for  immediate  use. 

PLANS   AND    DRAWINGS 

2.  The  plan,  profile,  and  cross-sections  on  file  in  the  office 
of  the  State  Commissioner  of  Public  Roads  and  at  the  office 

of County  Engineer New 

Jersey,  show  general  location,  profile,  details,  and  dimensions. 
The  work  will  be  constructed  in  all  respects   according  to  the 
above-mentioned  plan,  profile,  and  cross-sections,  which  form 
part  of  these  specifications. 


BROKEN-STONE   ROADS  127 

3.  Any  variation  of  location,  profile,  size,  and  dimensions 
from  that  shown  on  the  plan,  as  may  be  required  by  the  exi- 
gencies of  construction,  will,  in  all  cases,  be  determined  by  the 
engineer,  but  the  contractor  shall  not,  on  any  pretence,  save  that 
of  the  written  order  of  the  contracting  parties  and  the  State 
Commissioner  of  Public  Roads,  deviate  from  the  intent  of  the 
plan  or  specifications. 

4.  On  all  drawings,  figure  dimensions  are  to  govern  in  cases 
of  discrepancy  between  scale  and  figures. 

GRADING 

5.  Under  this  head  will  be  included  all  excavation  and  em- 
bankment required  for  the  formation  of  the  highway,  cutting  all 
ditches  or  drains  about  or  contiguous  to  the  road,  removing  all 
fences,  walls,  buildings,  trees,  poles,  or  other  encumbrances,  the 
excavation  and  embankment  necessary  for  reconstructing  cross 
or  branch  roads  or  entrances  to  dwellings  in  cases  where  they 
are  destroyed  or  interfered  with  in  the  formation  of  the  roadway, 
and  all  other  excavations  and  embankments  connected  with  or 
incidental  to  the  construction  of  the  said  road. 

EXCAVATION 

6.  The  roadway  to  the  widths  and  depths  as  shown  on  plans 
must  be  excavated  or  built  to  the  same  curvature  as  that  of  the 
surface  of  the  road  when  finished.     The  grade,  from  centre  to 
sides,  must  be  as  shown  on  plans. 

7.  The  earth  taken  from  any  cut  or  ditch  shall  be  deposited 
where  the  engineer  may  direct,  either  within  or  without  the  line 
of  the  road,  but  no  earth  shall  be  removed  from  the  line  of  the 
road  without  the  order  of  the  engineer. 

8.  The  grading  shall  be  completed  for  the  full  width  of  the 
road,  from  gutter  to  gutter,  before  any  macadamizing  is  com- 
menced. 


128  HIGHWAY   ENGINEERING 

EMBANKMENT 

9.  Material  taken  from  the  excavations,  except  when  other- 
wise directed  by  the  engineer,  shall  be  deposited  in  the  embank- 
ments, either  on  the  roadway  or  sidewalks.     Rejected  or  excess 
material  will  be  used  to  increase  the  width  of  the  embankments 
or  deposited  in  spoil  banks  or  waste  piles,  as  and  where  the 
engineer  may  direct. 

10.  When  there  is  not  sufficient  material  in  the  excavations  of 
the  road  to  form  the  embankments,  the  deficiency  must  be  sup- 
plied by  the  contractor  from  without  the  road.     The  character  of 
said  material  and  place  of  excavation  must  be  approved  by  the 
engineer. 

11.  The  embankments  will  be  formed  in  layers  of  such  depth, 
generally  one  (1)  foot,  and  the  material  deposited  and  distributed 
in  such  a  manner  as  the  engineer  may  direct,  the  required  al- 
lowance for  settling  being  added.     Each  layer  shall  be  carried 
across  the  entire  width  of  the  embankment  and  completed  before 
commencing  another,  and  this  method  shall  be  followed  with  each 
succeeding  layer  until  the  established  grade  is  reached. 

SLOPES 

12.  Slopes  in  both  embankment  and  excavation  shall  be  one 
and  one-half  (1J)  horizontal  to  one  (1)  vertical,  when  the  width 
of  the  road  will  permit;  if  the  road  is  too  narrow  to  allow  the 
full  slope  within  its  side  lines,  the  engineer  shall  not  calculate 
the  quantities,  either  in  embankment  or  excavation  beyond  said 
side  lines,  unless  the  required  ground  shall  be  first  dedicated  to 
the  public  in  writing  by  the  owner  or  owners  thereof. 

WIDTH   AND   DEPTH 

13.  The  construction  to  be inches  deep   and 

feet  wide,  as  shown  on  plan  and  detail  sheet. 


BROKEN-STONE   ROADS  129 

ROADWAY 

Sub  foundations. 

14.  When  the  excavations  and  embankments  have  been 
brought  to  a  proper  depth  below  the  intended  surface  of  the  road- 
way, the  cross-section  thereof  conforming  in  every  respect  to  the 
cross-section  of  the  road  when  finished,  the  same  shall  be  rolled 
with  a ton  roller  until  it  is inches  be- 
low the  intended  surface  of  the  road  and  is  approved  by  the 
engineer  and  supervisor.     If  any  depressions  form  under  such 
rolling,  owing  to  improper  material  or  vegetable  matter,  the 
same  shall  be  removed  and  good  earth  substituted,  and  the 
whole  re-rolled  until  thoroughly  solid  and  to  above-mentioned 
grade.     Water  must  be  applied  in  advance  of  the  roller  when,  in 
the  opinion  of  the  engineer  and  supervisor,  it  is  necessary. 

STONE  CONSTRUCTION 

Telford  Foundations 

15.  After  the  roadbed  has  been  formed  and  rolled,  as  above 
specified,  and  has  passed  the  inspection  of  the  engineer  and 
supervisor,  a  bottom  course  of  stone,  of  an  average  depth  of 
inches,  is  to  be  set  by  hand  as  a  close,  firm  pave- 
ment, the  stones  to  be  placed  on  their  broadest  edges  lengthwise 
across  the  road  in  such  manner  as  to  break  joints  as  much  as 
possible,  the  breadth  of  the  upper  edge  not  to  exceed  four  (4) 
inches.     The  interstices  are  then  to  be  filled  with  stone  chips, 
firmly  wedged  by  hand  with  a  hammer,  and  projecting  points 
broken  off.     No  stone  of  greater  length  than  ten  (10)  inches  or 
width  of  four  (4)  inches  shall  be  used,  except  each  alternate  stone 
on  outer  edge,  which  shall  be  double  the  length  of  the  others  and 
well  tied  into  the  bed  of  the  road.     All  stones  with  a  flat,  smooth 
surface  must  be  broken.     The  whole  surface  of  this  pavement 
must  be  subjected  to  a  thorough  settling  or  ramming  with  heavy 

9 


130  HIGHWAY   ENGINEERING 

sledge-hammers,  and  thoroughly  rolled  with  a ton 

roller.     No  stone  larger  than  two  and  one-half 

(2J)  inches  shall  be  left  loose  on  top  of  telford. 

MACADAM 

First  Course  of  Broken  Stone 

16.  After  the  roadbed  has  been  formed  and  rolled,  as  above 
specified,  and  has  passed  the  inspection  of  the  engineer  and  super- 
visor, the  first  layer  of  broken  stone,  consisting  of  two  and  one- 
half  (2J)  inch  stone,  or  stone  that  will  pass  through  a  ring  three 
(3)  inches  in  diameter,  shall  be  deposited  in  a  uniform  layer,  hav- 
ing a  depth  of inches,  and  rolled  repeatedly  with 

a ton roller  until   compacted   to   the 

satisfaction  of  the  engineer  and  supervisor.     No  stone  in  this 
course  shall  be  less  than  two  (2)  inches  in  length. 

17.  The  depth  of  loose  stone  in  this  and  all  other  courses 
must  be  measured  by  blocks  the  required  thickness  of  the  said 
loose  stone.     These  blocks  must  be  placed  at  frequent  intervals 
amid  the  loose  stone  when  being  spread. 

BINDER   BETWEEN   FIRST   AND   SECOND   COURSE    FOR   TEL- 
FORD   OR  MACADAM 

18.  On  the  first  course  of  stone  a  quantity  of 

binder  shall  be  spread  in  a  uniform  layer,  and  the  whole  rolled 
until  the  stones  cease  to  sink  or  creep  in  front  of  the  roller.     The 
quantity  and  quality  of  this  and  all  other  binding  shall  be  sub- 
ject to  the  approval  of  the  engineer  and  supervisor.     Water  must 
be  applied  in  advance  of  the  roller,  if  ordered  by  the  engineer  or 

supervisor. 

• 

SECOND   COURSE   OF   BROKEN   STONE   FOR  MACADAM   OR 
TELFORD 

19.  The  second  course  of  broken  stone  shall  consist  of  one 
and  one-half  (1J)  inch  stone;  that  is,  every  piece  of  stone  shall 


BROKEN-STONE   ROADS  131 

be  broken  so  that  it  can  be  passed  through  a  ring  two  (2)  inches 
in  diameter,  and  no  stone  shall  be  more  than  two  (2)  inches  or  less 
than  one  (1)  inch  long.  This  course  shall  be  spread  in  a  uniform 

layer inches  in  depth  and  rolled  until  thoroughly 

settled  into  place  to  the  satisfaction  of  the  engineer  and  super- 
visor. Water  must  be  applied  as  ordered  by  the  engineer  or 
supervisor. 

BINDER   ON   SECOND   COURSE    OF   STONE 

20.  Binder  on  this  course  of  stone  must  be  applied  in  the  same 
manner  as  binder  on  first  course  of  stone  (see  Art.  18),  as  directed 
by  engineer  and  supervisor. 

SURFACE 

21.  When  the  two  courses  are  rolled  to  the  satisfaction  of  the 
engineer  and  supervisor,  a  coat  of  fifty  (50)  per  cent  of  three- 
quarter  (f)  inch  stone  and  fifty  (50)  per  cent  of  screenings, 
properly  mixed,  is  to  be  spread  of  sufficient  thickness  to  make  a 
smooth  and  uniform  surface  to  the  road,  then  again  rolled  until 
the  road  becomes  thoroughly  consolidated,  hard  and  smooth. 

22.  Rolling  must  be  done  by  the  contractor  with  a 

ton roller,  approved  by  the  engineer. 

23.  Any  depressions  formed  during  the  rolling,  or  from  any 
other  cause,  are  to  be  filled  with  one  and  one-half  (1J)  inch 
stone,  or  three-quarter  (})  inch  stone,  or  both,  and  screenings, 
approved  by  the  engineer,  and  the  roadway  brought  to  the  proper 
grade  and  curvature  as  determined  by  him. 

24.  Water  must  be  applied  in  such  quantities  and  in  such 
manner  as  directed  by  the  engineer  or  supervisor. 

MANNER   OF   ROLLING 

25.  In  the  rolling  the  roller  must  start  from  the  side  lines  of 
the  stone  bed  and  work  toward  the  centre,  unless  otherwise 


132  HIGHWAY  ENGINEERING 

directed.  The  roller  shall  at  all  times  be  subject  to  the  direc- 
tions of  the  engineer  and  supervisor,  who  may,  from  time  to  time, 
direct  such  methods  of  procedure  as  in  their  opinion  the  neces- 
sities of  the  case  may  require. 

QUALITY   OF  MATERIAL 

26.  All  stones  must  be  as  nearly  cubical  as  possible,  broken 
with  the  most  approved  modern  stone-crushing  machinery,  free 
from  all  screenings,  earth,  and  other  objectionable  substances,  of 
uniform  size,  and  the  same  kind  and  quality,  or  equally  as  good 
in  every  particular  as  that  shown  in  the  engineer's  office.     The 
one  and  one-half  (1J)  inch   stone,  three-quarter  (f)  inch    and 
screenings  for  binder  and  final  finish  must  be  of  the  best  trap- 
rock,  free  from  loam  or  clay. 

27.  The  contractor  must  furnish  samples  to  the  engineer  of 
the  kind  of  stone  to  be  used  in  the  work  before  the  opening  of  the 
bids,  and  to  the  State  Commissioner  of  Public  Roads  before  the 
approval  of  the  contract  by  him. 

ENTRANCES   TO   DWELLINGS 

28.  All  driveways  leading  to  dwellings  along  the  road  shall  be 
macadamized  with  the  second  course  and  finished  in  the  same 
manner  as  prescribed  for  the  main  road.     The  macadamizing 
shall  be  carried  to  a  distance  of  not  more  than  six  feet  beyond  the 
gutter  line  of  the  road,  as  indicated  by  the  engineer's  stakes,  but 
in  no  case  shall  the  macadamizing  be  carried  beyond  the  side  line 
of  the  road  as  indicated  by  the  fences. 

SHOULDERING 

29.  A  shoulder  of  firm  earth  or  gravel  is  to  be  left  or  made  on 
each  side,  extending  at  the  same  grade  and  curvature  of  road  to 
side  ditches  or  gutters.     This  shoulder  is  to  be  rolled  according  to 
the  directions  of  the  engineer. 


BROKEN-STONE   ROADS  133 


COBBLE    GUTTERS 

30.  Cobble  gutters  shall  be  laid  from  station  number 

to  station  number The  cobbles  used  must  be  good, 

hard,  sound  stone.     Medium-sized  stone,  not  over  five-inch  face 
on  its  longest  diameter,  must  be  used,  except  for  centres  or  sides, 
where  eight-inch  cobbles  may  be  used.     The  cobbles  must  be 
bedded  in  not  less  than  six  inches  of  good,  sharp  sand  or  gravel, 
and  laid  with  the  longest  diameter  of  stone  parallel  with  the  road, 
and  thoroughly  rammed  into  shape  and  place.     All  stone  broken 
hi  ramming  must  be  removed  and  replaced  with  perfect  stone. 

SIDE   DITCHES   OR   GUTTERS 

31.  The  side  ditches  or  gutters  are  to  be  excavated  as  per 
stakes  furnished  by  engineer,  in  order  to  give  an  easy  flow  of 
water,  so  that  no  water  shall  be  left  standing  on  the  road  or  in  the 
ditches,  for  which  no  extra  payment  will  be  made. 

UNDERDRAINS 

32.  Underdrains,  if  found  necessary,  shall  be  constructed  by 

the  contractor  of  good inch tile,  laid  upon  a  board 

of  not  less  than  one  (1)  inch  in  thickness  and  six  (6)  inches  in 

width.    The  top  of  the  tile  shall  be  at  least inches 

deep,  unless  otherwise  directed  by  the  engineer,  the  joints  shall 
be  covered  with  salt  hay,  or  material  equally  as  good,  and  the 
trench  filled  with  pervious  earth.     These  drains  must  be  con- 
structed whenever  and  wherever  the  engineer  and  supervisor 
shall  decide. 

33.  When  directed  by  the  engineer,  a  stone  drain  may  be  used 
in  place  of  the  tile  drain.     A  trench  one  foot  wide  and  one  foot 
six  inches  deep  shall  be  excavated  below  the  subgrade,  said 
excavation  to  be  filled  with  loose  broken  stone  to  a  depth  re- 
quired by  the  engineer. 


134  HIGHWAY  ENGINEERING 


BROAD-TIRE   WAGONS 

34.  All  wagons  and  carts  used  during  the  construction  for 
hauling  stone,  earth,  or  any  other  material  must  have  tires  not 
less  than  three  and  one-half  (3i)  inches  in  width.. 

NO   EXTRA   PRICE 

35.  No  allowance  in  measure  of  depth  of  pavement  will  be 
made  on  account  of  any  material  which  may  be  driven  into  the 
roadbed  by  rolling.     The  pavement,  when  completed,  must  con- 
form to  the  grade  and  the  cross-sections,  and  be  satisfactory  to 
the  engineer  and  State  Commissioner  of  Public  Roads,  whose  de- 
cisions shall  be  final. 

36.  No  extra  work  will  be  paid  for  unless  the  price  has  been 
agreed  upon  between  the  contracting  parties,  including  the  State 
Commissioner  of  Public  Roads,  and  indorsed  upon  the  agree- 
ment witnessed  by  the  engineer. 

37.  All  clay  or  gravel  for  shouldering  or  binder  and  all  extra 
hauling  is  to  be  done  at  the  contractor's  expense. 

BIDS 

38.  Bids  will  only  be  received  under  these  specifications  for 
the  road  complete.     The  prices  per  yard  for  excavation,  telford, 
macadam,  etc.,  are  intended  for  the  use  of  the  engineer  in  making 
estimate  to  the  Board  of  Chosen  Freeholders  of  work  done.     No 
bid  will  be  received  in  which  all  of  the  following  items  are  not 
filled  out: 

(1)  Price  per  cubic  yard  for  earth  excavations,   without 
classification,  as  per  cross-sections  throughout  the  length  and 
width  of  the  road. 

(2)  Price  per  cubic  yard  for  any  necessary  earth  excavations 
and  removing  material  without  classification  and  measured  in 
excavation,  not    included    in  the   length    and    width  of   the 
road. 


BROKEN-STONE   ROADS  135 

(3)  Price  per  square  yard  for  macadam  driveways  to  dwell- 
ings. 

(4)  Price  per  square  yard  for  telford  road  complete. 

(5)  Price  per  square  yard  for  macadam  road  complete. 

(6)  Price  per  square  yard  for  cobble  gutters  complete. 

(7)  Price  per  lineal  foot  for  underdrains,  furnishing  all  labor 
and  material. 

(8)  Price  (lump)  for  the  whole  road  complete,  according  to 
above  specifications  and  plans. 

ESTIMATE   OF  QUANTITIES 

39.  (1)  Excavation,  earth cubic  yards. 

(2)  Extra  excavation cubic  yards* 

(3)  Macadam  driveways  ....  square  yards,  as  specified. 

(4)  Telford  square  yards,  as  specified. 

(5)  Macadam  square  yards,  as  specified. 

(6)  Cobble  gutters square  yards,  as  specified. 

(7)  Underdrains    lineal  feet. 

(8)  

40.  These  quantities  are  the  result  of  calculation,  but  are  to 
be  considered  as  approximate.     The  county  will  not  be  respon- 
sible for  any  excess  in  above  quantities,  should  any  occur.     The 
contractor  is  expected  to  satisfy  himself  as  to  the  nature,  charac- 
ter, and  quantity  of  the  labor  and  material  required  by  a  personal 
examination  of  the  work  contemplated. 

CHECK  ACCOMPANYING   BIDS 

41.  Bids  shall  be  accompanied  with  a  certified  check,  payable 
to  the  order  of  the  Director  of  the  Board  of  Chosen  Freeholders, 
in  the  sum  of  one  thousand  dollars  ($1,000),  as  a  guaranty  that 
if  the  contract  shall  be  awarded  to  him  he  will,  when  required  by 
said  board,  execute  an  agreement  in  writing  to  perform  the  work 
according  to  the  specifications.     Upon  failure  by  the  contractor 
to  enter  into  said  agreement  with  the  said  Board  of  Chosen  Free- 


136  HIGHWAY  ENGINEERING 

holders,  said  certified  check  shall  be  forfeited  and  considered  as 
liquidated  damages. 

LIABILITIES   OF   CONTRACTOR 

42.  He  shall  maintain  sufficient  guards  by  day  and  night  to 
prevent  accidents  from  travel,  and  will  be  liable  for  any  damage 
which  may  arise  from  his  neglect  to  do  so,  or  from  any  omission  on 
his  part. 

43.  He  shall  keep  the  road  sprinkled  until  the  certificate  of 
completion  by  the  engineer  is  given. 

44.  He  is  to  commence  and  prosecute  the  work  upon  the  road 
at  the  end  farthest  from  the  source  of  supply  of  broken  stone,  un- 
less otherwise  ordered  by  the  engineer,  within days  from 

and  after  the  signing  of  the  contract,  and  shall  continue  work 
thereon  until  completion,  except  as  herein  provided. 

45.  He  further  agrees  to  complete  the  same  on  or  before  the 

day    of A.D Twenty  dollars   for  each 

day  that  the  work  shall  remain  uncompleted,  after  the  time  al- 
lowed by  contract,  may  be  deducted,  as  liquidated  damages, 
from  any  moneys  due  the  contractor,  unless  otherwise  agreed 
upon  by  the  Board  of  Chosen  Freeholders,  after  presentation  of 
certificate  of  the  engineer  recommending  the  extension  of  the 
time  limit  of  completion. 

46.  The  contractor  shall  keep  the  finished  roadway,  earth- 
work, side  ditches,  and  underdrains  in  repair  for  the  period  of 
one  year  from  the  date  of  its  completion  and  acceptance,  and,  in 
addition  thereto,  for  as  much  longer  as  for  any  period  or  periods 
during  said  year  it  shall  be  out  of  proper  condition.     If,  during 
that  time,  the  roadway  or  any  part  of  the  work  shall,  in  the  judg- 
ment of  the  engineer  and  the  Board  of  Chosen  Freeholders,  re- 
quire repairing,  and  they  shall  duly  notify  the  contractor  to  make 
such  repairs  as  required,  and  the  contractor  should  refuse  or 
neglect  to  do  so  to  the  satisfaction  of  the  said  engineer  and  the 
Board  of  Chosen  Freeholders,  within  five  days  from  the  date  of 


BROKEN-STONE  ROADS  137 

service  of  notice,  then  the  said  engineer  and  the  Board  of  Chosen 
Freeholders  shall  have  the  right  to  have  the  work  done  properly 
by  other  parties  and  recover  the  cost  for  the  same  from  the  said 
contractor  or  his  surety. 

47.  The  contractor  will  be  required  to  preserve  all  stakes  and 
bench-marks  made  and  established  on  the  line  of  work  until  duly 
authorized  by  the  engineer  to  remove  the  same.     All  stakes  or 
bench-marks  disturbed  or  removed  by  the  contractor  or  his 
agents  without  the  permission  of  the  engineer  shall  be  replaced 
at  the  expense  of  the  contractor. 

48.  The  contractor  shall  not  disturb  the  position  of  title- 
stones  (the  corners  of  properties  adjacent  to  the  road),  but 
where  they  appear  he  will  either  lift  or  lower  them,  under  the 
personal  supervision  of  the  engineer. 

49.  The  contractor  must  also  preserve  the  roadway  on  which 
he  is  working  from  needless  obstruction,  and  where  necessary 
he  must  construct  safe  and  commodious  crossings,  to  be  main- 
tained in  good  order.     He  shall  afford  all  proper  and  reas- 
onable   means    for    the    accommodation    of   the  public,   and 
leave  the  roadway  complete  in  every  manner  ready  for  im- 
mediate use. 

50.  All  loss  or  damage  arising  from  the  nature  of  the  work  to 
be  done,  or  from  any  unforeseen  or  unusual  obstruction  or  dif- 
ficulty which  may  be  encountered  in  the  prosecution  of  said  work, 
or  from  the  action  of  the  elements,  shall  be  sustained  by  the 
contractor. 

PROVISION   FOR  DRAINAGE 

51.  If  it  is  necessary  in  the  prosecution  of  the  work  to  inter- 
rupt or  obstruct  the  natural  drainage  of  the  surface,  or  the  flow 
of  artificial  drains,  the  contractor  shall  provide  for  the  same,  dur- 
ing the  progress  of  the  work,  in  such  a  way  that  no  damage  shall 
result  to  either  public  or  private  interest.     He  shall  be  held  liable 
for  all  damages  which  may  result  from  any  neglect  to  provide  for 


138  HIGHWAY   ENGINEEKING 

either  natural  or  artificial  drainage,  which  he  may  have  inter- 
rupted. 

RIGHT  TO  BUILD  BRIDGES,   CULVERTS,   ETC.,   AND  SUSPENSION  OF 

WORK 

52.  The  right  of  the  county  to  build  bridges,  culverts,  lay 
pipes  or  other  appurtenances  in  said  road  during  the  progress  of 
the  work,  is  expressly  reserved,  as  well  as  suspending  the  work, 
x)r  any  part  thereof,  during  the  construction  of  the  same,  for  the 
purposes  above  stated,  without  further  compensation  to  the  con- 
tractor for  such  suspension  than  an  extension  of  time  for  com- 
pleting the  work  as  much  as  it  may  have  been  delayed. 

STOPPING   WORK   ON   ACCOUNT   OF   WEATHER 

53.  The  State  Commissioner  of  Public  Roads,  engineer,  or 
supervisor  may  stop  any  portion  of  the  work,  if,  in  their  judg- 
ment, the  weather  is  such  as  to  prevent  the  same  being  done 
properly.     No  allowance  of  any  kind  will  be  made  for  such  stop- 
page, except  an  extension  of  the  time  for  the  completion  of  the 
work  as  herein  provided. 

ABANDONMENT   OF   CONTRACT 

54.  If  at  an}7  time  the  work  under  contract  should  be  aban- 
doned, or  if  at  any  time  the  engineer  should  judge  and  so  certify 
in  writing  that  said  work,  or  any  part  thereof,  is  unnecessarily 
delayed,  or  that  the  contractor  is  wilfully  violating  any  of  the 
conditions  or  covenants  of  this  contract,  or  is  executing  the  same 
in  bad  faith,  then,  in  that  case,  the  Board  of  Chosen  Freeholders 
shall  notify  the  said  contractor  to  discontinue  all  work  under  this 
contract.     They  may  employ  other  parties  to  complete  the  work 
in  such  manner  as  they  may  decide,  and  use  such  material  as  may 
be  procured  upon  the  line  of  aforesaid  work,  and,  if  necessary, 
procure  other  material  for  its  completion,  and  charge  the  ex- 
pense of  the  said  labor  and  material  to  the  contractor,  which 


BROKEN-STONE   ROADS  139 

expense  shall  be  deducted  from  any  moneys  due  him  under  con- 
tract. In  case  these  expenses  shall  exceed  the  sum  which  would 
have  been  payable  under  contract,  if  the  same  had  been  com- 
pleted by  said  contractor,  he  or  his  bondsmen  shall  pay  the 
amount  of  the  excess  to  the  Board  of  Chosen  Freeholders,  on 
notice  from  the  engineer. 

ENGINEER 

55!  The  engineer  shall  be  selected  or  appointed  by  the  Board 
of  Chosen  Freeholders  and  paid  by  it.  He  shall  furnish  all 
surveys,  profiles,  plans,  specifications,  and  estimates  of  quantities 
of  all  kinds  before  specifications  are  signed,  and  in  such  a  clear 
manner  that  lump  bids. can  be  made  upon  the  work.  He  shall 
furnish  all  lines  and  grades  required  for  the  completion  of  the 
work.  He  shall  furnish  estimates  for  quantities  of  work  done 
before  partial  payments  can  be  made,  the  quantity  of  road  laid 
being  determined  by  surface  measurements.  Should  any  differ- 
ence arise  between  the  contracting  parties  as  to  the  meaning  or 
intent  of  these  specifications,  his  decisions  on  these  matters  are 
to  be  final  and  conclusive.  The  work  is  to  be  done  according  to 
his  directions,  and  if  any  material  of  which  he  does  not  approve 
is  brought  upon  the  road,  it  is  to  be  removed  at  the  expense  of  the 
contractor.  If  the  contractor  fails  or  neglects  to  do  any  part  of 
the  work  as  specified  or  as  directed  by  the  engineer,  then,  in  that 
case,  all  other  work  shall  be  discontinued,  on  notice  from  the 
engineer  to  the  contractor,  or  to  the  superintendent  or  foreman  in 
charge  of  the  work  for  the  contractor,  until  such  time  as  the  work 
complained  of  has  been  done  to  the  satisfaction  of  the  engineer, 
and  the  contractor  will  not  be  entitled  to  or  allowed  any  compen- 
sation or  extension  of  time  for  such  discontinuation  or  suspen- 
sion of  the  work. 

SUPERVISOR 

56.  Nothing  in  these  specifications  relating  to  the  duties  of  the 
engineer  shall  be  taken  or  construed  in  any  manner  to  conflict 


140  HIGHWAY   ENGINEERING 

with  the  duties  of  the  supervisor,  as  specifically  set  forth  in  the 
act  entitled  "  An  act  to  provide  for  the  permanent  improve- 
ment of  public  roads  in  this  State,"  approved  March  27th,  1905, 
but  they  shall  cooperate  as  far  as  oracticable. 

INCOMPETENT   WORKMEN 

57.  The  contractor  shall  employ  competent  men  to  do  the 
work,  and  whenever  the  engineer  and  supervisor  shall  inform 
him,  or  his  representative  in  charge,  in  writing,  that  any  man  on 
the  work  is  unfitted  for  the  place,  or  is  working  contrary  to  the 
provisions  of  the  specifications  or  the  instructions  of  the  engineer 
and  supervisor,  he  shall  thereupon  be  discharged. 

INSPECTION 

58.  All  directions  and  determinations  necessary  to  give  due 
and  full  effect  to  any  of  the  provisions  of  these  specifications  shall 
be  given  by  the  engineer  and  supervisor. 

59.  All  material  and  workmanship  of  any  kind  shall  be  sub- 
ject at  all  times  to  the  inspection  of  the  engineer  and  supervisor. 
Whenever  unfaithful  and  imperfect  work  is  discovered,  it  shall  be 
immediately  repaired  or  replaced  by  the  contractor,  after  due 
notification  from  the  engineer  and  supervisor. 

SUBLETTING   OF   CONTRACT 

60.  The  contractor  shall  not  assign  or  sublet  any  portion  of 
this  contract  without  the  consent  of  the  Board  of  Chosen  Free- 
holders and  the  State  Commissioner  of  Public  Roads. 

PAYMENTS 

61.  .'.'."...".  . monthly  payments  will  be  made  by  the  Board  of 
Chosen  Freeholders  to  the  contractor  for  work  performed,  upon 
presentation  by  him  of  the  proper  certificates  of  the  engineer  and 
supervisor,  in  a  sum  not  to  exceed  eighty  per  cent  of  the  amount 
then  due,  together  with  releases  from  all  liens,  if  required.     Fif- 


BROKEN-STONE    ROADS  141 

teen  per  cent  will  be  paid  at  the  completion  of  the  work  and  the 
acceptance  of  the  same  in  writing  by  the  Board  of  Chosen  Free- 
holders and  the  State  Commissioner  of  Public  Roads.  The 
remainder,  or  five  per  cent,  will  be  retained  by  the  Board  of 
Chosen  Freeholders  for  a  period  of  one  year  as  security  for  the 
faithful  performance  of  Article  46. 

BOND   OF   CONTRACTOR 

62.  The  contractor  will  be  required  to  execute,  within  thirty 
days  of  giving  of  contract,  a  bond  in  such  sum  and  with  such 
securities  as  shall  be  approved  by  the  Board  of  Chosen  Freehold- 
ers, conditioned  for  the  faithful  performance  of  the  contract,  to 
indemnify  and  save  harmless  the  Board  of  Chosen  Freeholders 
from  all  suits  or  actions  of  any  name  or  description  brought 
against  them  on  account  of  any  act  or  omission  of  the  contractor 
or  his  agents,  and  for  the  faithful  performance  of  the  contract  by 
the  contractor.     Said  bond  shall  be  in  a  sum  of  not  less  than  the 
estimated  cost  of  the  road  when  completed.     Any  change  made 
in  the  plans,  specifications,  agreements,  or  quantities  without 
the  consent  of  the  bondsmen  shall  in  no  way  vitiate  said  bond. 
The  contractor  hereby  further  agrees  that  so  much  of  the  money 
due  him,  under  and  by  virtue  of  this  agreement,  as  shall  be  con- 
sidered necessary  by  the  Board  of  Chosen  Freeholders,  may  be 
retained  by  them  until  all  such  suits  or  claims  for  damages  afore- 
said shall  have  been  settled,  and  evidence  to  that  effect  furnished 
to  the  satisfaction  of  the  Board  of  Chosen  Freeholders. 

CONTRACTOR  TO  INSURE  PAYMENT  FOR  LABOR,  MATERIAL,  ETC.,  ON 
FINAL    ESTIMATE 

63.  The  contractor  must  also  furnish  the  engineer  with  satis- 
factory evidence  that  all  persons  who  did  work,  or  furnished 
material  for  this  contract,  or  who  have  sustained  damage  or  in- 
jury by  reason  of  any  act,  omission,  or  carelessness  on  his  part 
or  his  agents  in  the  prosecution  of  the  work,  have  been  duly  paid 


142  HIGHWAY   ENGINEERING 

or  secured.  He  shall  also  give  notice  to  the  engineer  within  ten 
days  after  the  completion  of  the  work,  and  before  final  estimate 
is  made  that  any  balance  for  such  work  or  materials,  or  compen- 
sation for  such  damages  due,  has  been  fully  paid  or  released. 

64.  The  right  is  reserved  to  reject  any  or  all  bids,  if  deemed  to 
the  interest  of  the  county  or  State. 

County  Engineer. 

Approved  this ,  A.D ,  by  resolution  of  the 

Board  of  Chosen  Freeholders  of  the  county  of 

Director  of  Board  of  Chosen  Freeholders. 

Clerk  of  Board  of  Chosen  Freeholders. 

OFFICE  STATE  COMMISSIONER  OF  PUBLIC  ROADS,  TRENTON,  N.  J. 

I  have  this  day  carefully  read  and  examined  the  foregoing 
specifications,  and  the  same  are  hereby  approved. 

Any  departure  from  these  specifications  must  have  the 
written  consent  of  the  State  Commissioner  of  Public  Roads. 

Given  under  my  hand,  this ,  A.D.  190 

State  Commissioner  of  Public  Roads. 


CHAPTER   V 

MISCELLANEOUS    ROADS 

BURNT-CLAY   ROADS 

IN  the  Mississippi  valley,  where  road  material  is  not  only 
scarce  but  expensive,  recourse  has  been  had  to  burning  the  clay, 
of  which  the  roads  are  in  a  great  measure  formed,  to  produce  a 
harder  and  better  surfacing.  During  the  dry  season,  when  there 
is  but  little  moisture  in  the  soil,  the  material  is  cut  from  the 
roadway  in  blocks  to  the  depth  of  about  2  ft.  and  piled  so  as  to 
form  an  enclosure  8  to  10  ft.  sq.  After  this  has  thoroughly 
dried  out,  brush  and  wood  are  placed  inside,  more  clay  is  placed 
on  top  to  completely  enclose  it,  and  the  burning  of  the  clay  begun. 
The  hardened  material  resulting  from  this  burning  is  broken  up 
into  small  fragments  and  used  as  a  covering  to  the  roadway.  In 
the  wet  season,  when  the  roadway  would  be  particularly  soft,  it 
is  very  satisfactory  in  that  it  keeps  the  vehicles  from  breaking 
through  to  the  less  solid  material  below. 

CORDUROY    ROADS 

A  corduroy  or  log  road  derives  its  name  from  the  fact  that  in 
appearance  it  closely  resembles  the  material  of  that  name, 
consisting  as  it  does  of  a  succession  of  ridges  and  hollows. 
These  roads  are  designed  to  carry  traffic  over  naturally  wet  and 
soft  ground,  such  as  swamps  and  marshes,  where  drainage  is 
either  impossible  or  prohibitive  because  of  cost.  They  are 
formed  by  placing  logs  side  by  side,  with  the  length  perpendicular 
to  the  axis  of  the  road,  upon  a  roughly  prepared  foundation  of  the 
natural  soil.  Sometimes  the  logs  are  held  in  place  by  longitudi- 
nal stringers  being  spiked  to  the  ends,  sometimes  the  spaces  are 

143 


144 


HIGHWAY   EXGINEERING 


filled  with  smaller  poles  to  make  a  more  even  surface,  and  some- 
times upon  the  timber  is  placed  sod  or  earth  to  reduce  the  tractive 
resistances.  Crude  as  these  roads  are,  in  sparsely  settled  dis- 
tricts they  often  furnish  the  only  solution  of  keeping  a  road  open, 
particularly  in  the  wet  season. 

OILED    ROADS 

The  first  application  of  oil  to  a  road  surface  was  made  as  an 
experiment  in  1898,  in  Los  Angeles  County,  Cal.,  for  the  purpose 


FIG.  49.— Road  Through  Deep  Sand. 

of  determining  whether  or  not  oil  possessed  properties  that  would 
cause  it  to  lay  dust.  With  that  object  in  view  it  has  since  been 
employed  quite  successfully  on  many  miles  of  road  in  California, 
and  experimentally  in  New  Jersey,  Massachusetts,  Pennsylvania, 
Indiana,  Colorado,  and  the  District  of  Columbia;  and  in  foreign 
countries,  in  England,  France,  and  Switzerland. 


MISCELLANEOUS   ROADS 


145 


The  only  object  in  the  first  experiments  was  to  determine  if 
oil  would  lay  the  dust,  which  the  results  quite  conclusively  proved ; 
but  other  and  greater  advantages  besides  this  have  since  been 
discovered  by  its  continued  use.  The  deep  seal  brown  color 
produced  by  it  is  very  restful  to  the  eye,  but  more  particularly  it 
acts  as  a  binder  of  the  loose  particles  of  dust  and  stone  on  the 
road  surface,  forming  a  sort  of  tough  and  hard  crust  somewhat 
similar  to  asphalt.  When  the  crust  is  thin  it  has  been  observed 


FIG.   50.— Same  Road,  after  Oiling,  Has  a  Hard  Smooth  Crust. 

that  the  wheels  quickly  cut  into  it,  especially  in  wet  weather; 
but  experience  has  taught  that  with  the  oil  sinking  to  a  depth  of 
three  inches  or  more,  this  is  prevented. 

Rains  seem  to  have  no  effect  upon  such  roads,  for  the  surface 
is  impervious;  and  in  California,  where  the  storms  are  fre- 
quently torrential  in  character,  they  have  been  found  to  with- 

10 


146 


HIGHWAY    ENGINEERING 


stand  them  almost  without  a  sign  of  deterioration.  Unlike  as- 
phalt pavements,  which  during  hot  weather  show  the  effect  of 
heat  by  softening,  oiled  roads  remain  as  hard  and  firm  as  in 
cold  weather. 

All  petroleums  will  lay  the  dust,  but  oils  with  an  asphalt  base 
are  found  to  be  best  suited  to  the  purpose,  not  only  because  they 
prevent  the  dust  nuisance,  but  because  the  asphalt  in  them  acts 
as  a  most  excellent  binder  of  the  small  particles  which  lie  on  the 


FIG.  51.— Sections  of  Oiled  Crusts  from  Three  Oiled  Roads. 

surface  and  go  to  form  the  crust.     For  this  reason  the  higher  the 
percentage  of  asphaltum  in  the  oil  the  better. 

Previously  it  was  considered  good  practice  to  apply  the  oil 
when  the  surface  was  moist,  but  experience  has  taught  that  the 
road  should  be  perfectly  dry  to  secure  the  best  results.  Heating 
also  is  not  now  considered  necessary.  It  is  true  that  when  the 
oil  is  heated  the  ground  absorbs  it  more  quickly,  but  the  expense 
attached  to  this  operation  hardly  warrants  the  outlay. 


MISCELLANEOUS   ROADS  147 

Before  the  oil  is  applied  the  road  bed  should  be  graded,  given 
a  crown  of  about  one-half  inch  per  foot,  sprinkled  with  water, 
rolled  with  a  light  roller  to  secure  a  uniform  consistency  in  the 
ground  and  a  consequent  uniform  absorption  of  oil,  and  then 
allowed  to  dry  out  thoroughly.  After  this  a  toothed  harrow, 
the  teeth  of  which  are  three  inches  long,  should  be  drawn  over 
the  surface  to  break  it  up,  so  that  when  the  oil  is  applied  it  will 
readily  combine  to  form  a  crust  of  this  thickness. 

If  the  surfacing  material  is  too  hard,  as  in  macadam  pave- 
ments, to  permit  of  this,  then  a  layer  of  sand,  earth,  or  gravel 
must  be  laid  about  three  inches  deep,  and  the  oil  sprinkled  over 
this.  During  the  application  and  until  the  soil  has  thoroughly 
absorbed  the  oil,  all  traffic  is  prohibited  from  the  use  of  the  road- 
way. The  oil  is  spread  by  a  specially  constructed  tank  cart,  such 
as  shown  in  the  figure. 

Without  any  preparation  whatever  the  oil  is  often  applied 
to  a  road,  but  the  results  are  not  nearly  so  satisfactory. 
Particular  care  should  be  taken  on  improved  roads  to  re- 
move all  loose  material  on  the  surface,  so  that  the  oil  will 
reach  the  body  of  the  road,  and  not  merely  lie  on  the  surface 
in  the  form  of  an  oily  mud  to  be  easily  scattered  by  the 
wheels  of  vehicles. 

"  In  what  is  known  as  the  De  Camp  machine  the  distributor 
is  mounted  on  separate  wheels  and  coupled  to  the  rear  of  the 
tank  wagon,  the  slip  tongue  being  removed.  The  oil  runs 
from  the  tank  through  a  flexible  hose.  It  has  an  oil  reservoir 
and  three  sets  of  fingers.  The  first  set  makes  furrows  just  ahead 
of  the  oil-discharging  pipes.  The  second  set  of  fingers  (or  curved 
teeth)  covers  up  the  oil,  and  a  third  set  stirs  up  the  combination 
of  oil  and  dirt.  There  is  also  a  drag  to  crush  any  globules  or 
chunks  which  may  tend  to  form.  When  oil  is  being  distributed 
the  second  and  third  sets  of  fingers  and  the  drag  are  raised  from 
the  ground  by  hooks.  After  the  oil  is  distributed  this  machine  is 
detached  from  the  tank,  the  slip  tongue  put  in,  and  the  machine- 


148 


HIGHWAY   ENGINEERING 


dragged  back  and  forth  over  the  oiled  road  until  the  oil  has  been 
thoroughly  incorporated  with  the  road  material." 

After  from  twenty-four  to  forty-eight  hours  the  road  may  be 
thrown  open  to  traffic,  but  during  that  period  horses  and  wagons 
should  be  positively  prohibited  from  the  street. 

In  macadam  pavements,  where  the  surface  is  hard,  the  oil  is 


FIG.  52.— Road  Oiler. 


put  on  hot,  so  that  some  may  readily  sink  into  the  pavement  while 
that  which  is  left  is  sprinkled  and  incorporated  with  sand  which 
forms  a  hard,  even  crust  on  the  macadam  and  gives  excellent  re- 
sults in  that  it  produces  an  impervious  covering  and  at  the  same 
*time  protects  the  stone  from  wear. 


MISCELLANEOUS  ROADS  149 

The  quantity  of  oil  required  for  a  16  ft.  roadway  will  vary 
from  250  to  400  bbls.  of  42  gals.,  per  mile,  depending  upon  the 
thickness  of  the  crust,  the  porosity  of  the  soil,  and  the  percentage 
of  asphaltum  in  the  oil.  The  number  of  applications  depends 
upon  the  porosity  of  the  oil. 

Repairs  are  made  by  preparing  a  sort  of  mortar  of  oil  and 
sand,  and  filling  the  depressions  or  holes  with  this,  after  which  it 
is  well  rammed. 

"  It  frequently  happens  that  travel  follows  the  same  track, 
and  the  narrow  tires  and  feet  of  the  horses  wear  depressions.  It 
is  important  to  correct  these  and  reshape  the  road  at  least  once  a 
year.  It  has  been  found  that  an  ordinary  blade  road  grader  will 
not  do  this  successfully,  but  will  tear  up  the  oiled  crust  and  des- 
troy it.  The  White  smoother  is  a  device  for  shaving  off  elevations 
and  filling  up  depressions  in  an  oiled  crust.  It  consists  of  a  pair 
of  runners  16  ft.  long  and  4  ft.  apart.  Between  them,  at  the 
front  end,  are  set  on  a  slant  backward  obliquely  to  the  left,  3 
rows  of  }  in.  steel  harrow  teeth,  so  adjusted  that  they  shave 
along  lines  just  1  in.  apart.  As  their  edges  get  dull,  the  teeth  can 
receive  a  quarter  or  half  turn,  and  their  height  from  the  ground 
can  be  regulated.  There  is  also  a  blade  set  obliquely  which 
scrapes  off  the  shavings  made  by  the  harrow  teeth.  These  shav- 
ings, confined  by  the  two  runners  and  the  blade,  naturally  seek 
the  depressions.  In  the  left-hand  runner  is  an  opening,  through 
which  any  surplus  shavings  are  forced  out  toward  the  centre  of 
the  road,  thus  tending  to  raise  the  crown.  There  are  wheels 
on  the  sides  upon  which  the  machine,  with  runners  raised 
from  the  ground,  travels  when  being  moved  from  one  place 
to  another,  and  a  steering  gear  by  means  of  which  the  operator 
readily  controls  its  direction.  A  road  reshaped  with  this 
machine,  treated  with  a  light  sprinkling  of  oil  and  a  thin 
sheet  of  sand,  and  rolled,  resembles  a  city  asphalt  street 
when  first  laid." 


150  HIGHWAY    ENGINEERING 

SHELL  ROADS 

In  the  Chesapeake-Bay  district,  where  oysters  are  so  plentiful 
and  road  material  somewhat  scarce,  it  has  been  found  that  the 
shells  serve  quite  satisfactorily  as  a  road  metal.  The  shells  are 
easily  crushed  by  traffic  and,  possessing  an  extremely  high  ce- 
mentation factor  due  to  the  lime,  readily  bind  together  to  form 
a  roadway  of  more  than  ordinary  value.  The  disadvantage  of 
such  roads  is  that  the  material  being  so  soft,  is  quickly  ground 
to  powder,  which  the  wind  or  the  rain  readily  carries  away. 

In  Maryland  as  many  as  250  miles  of  these  roads  have  been 
built  at  a  very  reasonable  figure.  Where  the  shells  are  plentiful 
they  will  average  1J  cts.  a  bushel,  and  a  road  15  ft.  wide  will 
require  about  45,000  bushels  per  mile. 

"  As  with  any  road,  before  applying  the  surfacing,  the  road- 
bed for  the  shell  road  should  be  first  graded  and  given  the  proper 
cross-section.  If  there  is  a  wet  springy  soil,  drains  should  also 
be  provided.  Before  the  shells  are  put  on,  the  roadbed  should 
be  rolled  firm  and  hard.  If  over  a  stiff  clay  soil  which  becomes 
sticky  in  wet  weather  and  holds  moisture,  a  layer  of  three  or  four 
inches  of  sand  should  be  first  spread  on  the  clay  road.  Shells  may 
then  be  spread,  sprinkled  with  sand,  and  rolled  with  a  light 
roller.  Experience  has  shown  that  the  shell  roads  constructed 
over  a  clay  soil  have  broken  through  more  easily  than  those  over 
a  sandy  soil.  This  is  the  result  of  non-drainage  of  the  water 
which  is  held  in  the  clay.  To  assist  in  compacting  the  shells, 
as  in  the  construction  of  a  stone  road,  a  shoulder  of  earth 
should  be  formed  at  the  sides  to  prevent  the  shells  from  spread- 
ing." When  compacted,  the  road  forms  an  impervious  cover- 
ing, and  would  answer  well  as  a  foundation  for  a  thin  layer  of 
stone. 

SLAG    ROADS 

Slag  roads  need  but  little  mention  since  they  are  used  only  to 
a  limited  degree,  and  then  only  in  the  vicinity  of  smelting 


MISCELLANEOUS  ROADS  151 

plants  where  it  may  be  desirable  to  dispose  of  such  material. 
Slag  usually  contains  a  large  percentage  of  silica,  thus  making  a 
road  surface  built  of  it  extremely  hard,  but  frequently  it  lacks  in 
binding  properties.  Slags  running  high  in  lime,  however,  possess 
this  characteristic  and  produce  a  very  satisfactory  hard  and 
smooth  surface.  The  dust,  also,  seems  to  act  like  a  cement, 
binding  the  fragments  together  and  growing  harder  and  harder. 

SHALE   ROADS 

The  argillaceous  shales  are  unsuited  for  road-building  pur- 
poses, as  they  quickly  grind  to  powder  and  are  turned  to  mud  by 
the  action  of  the  atmosphere  and  rain,  but  in  the  State  of  New 
York  the  arenaceous  shales,  possessing  some  of  the  qualities  of 
soft  sandstone,  have  in  cases  been  the  means  of  affording  a  cheap 
and  satisfactory  roadway. 

The  material  is  obtained  close  at  hand  and,  after  the  roadway 
has  been  graded  properly,  from  8  to  10  ins.  is  spread  and  com- 
pacted by  rolling  with  a  10  ton  roller.  The  interstices  are  filled 
with  gravel,  a  thin  layer  of  it  spread  over  the  surface,  and  the 
road  is  then  sprinkled  and  rolled  again. 

COAL-SLACK   ROADS 

Coal  slack  is  the  fine  material  resulting  from  the  handling 
of  coal  and  the  disintegration  of  soft  coal.  It  is  commonly  used 
in  coal-mining  sections  for  road  purposes  where  it  is  often  a  prob- 
lem to  dispose  of  it. 

As  the  material  is  easily  ground  to  a  powder  and  blown  away, 
it  is  better  suited  to  light,  rather  than  heavy  traffic. 

CHARCOAL   ROADS 

Charcoal  roads  are  only  built  in  the  lumber  districts  where 
timber  is  both  cheap  and  plentiful.  They  are  constructed  as 
follows :  the  trees  are  felled  and  the  trunks  piled  lengthwise  along 


152  HIGHWAY   ENGINEERING 

the  centre  of  the  road  to  the  height  of  about  6  ft.,  being  9  ft.  wide 
at  the  base  and  2  at  the  top.  The  timber  is  then  completely 
covered  over  with  straw,  earth,  or  sod,  and  the  wood  burned. 
When  completely  charred,  the  covering  is  removed  and  the  char- 
coal spread  over  the  road  surface  to  a  depth  of  about  two  feet 
at  the  centre  and  one  foot  at  the  side.  It  is  claimed  that  such 
roads  are  remarkably  free  from  mud  and  dust.  For  the  sections 
they  are  intended  to  serve  such  roads  would  seem  to  fill  most  of 
the  requirements,  and  cost  about  one-quarter  that  of  a  good 
stone  or  gravel  road. 

PLANK   ROADS 

These  roads  are  generally  constructed  of  a  width  of  8  ft.,  as 
with  wider  ones  the  traffic  tends  to  follow  the  middle  of  the  road 
and  hence  produce  undue  wear.  If  8  ft.  is  not  sufficient,  16  ft. 
may  be  used,  but  in  this  case  there  should  be  two  separate  lines 
rather  than  one.  This  may  be  secured  by  spiking  down  a  6  X  6 
stringer  in  the  centre  of  the  road  parallel  to  the  axis,  with 
spaces  for  turnouts  every  100  ft. 

The  planks,  8  ft.  long,  9  to  12  ins.  wide,  and  3  to  4  ins.  thick, 
are  laid  perpendicular  to  the  line  of  traffic  upon  sills  which  are 
firmly  bedded  upon  an  even  foundation  of  the  natural  soil. 
These  sills  consist  of  planks  15  to  20  ft.  long,  12  ins.  wide,  and  4 
iris,  thick,  laid  flat,  placed  parallel  to  the  axis  of  the  road,  and 
spaced  4  to  5  ft.  centre  to  centre  so  that  the  wheels  will  be  di- 
rectly over  the  stringers.  They  should  break  joints  to  prevent 
the  soil  at  these  points  from  sinking. 

The  ends  of  the  plank  are  not  arranged  in  a  straight  line,  but 
every  third  or  fourth  is  offset  a  few  inches  to  form  a  shoulder 
and  permit  teams  to  turn  on  or  off  the  planked  way. 

Sometimes  the  planks  are  spiked  down,  but  this  is  not  essen- 
tial if  they  rest  upon  a  good  even,  firm,  and  dry  foundation  of 
natural  soil  between  the  sills.  Occasionally  earth  or  gravel  will 
be  spread  over  the  planks  to  prevent  their  too  rapid  wear,  and 


MISCELLANEOUS   ROADS  153 

also  form  a  firmer  covering  as  grit  is  forced  into  the  fibres  and 
makes  the  road  hard. 

Where  a  plank  road  exists  beside  one  of  dirt,  drainage  is 
secured  by  sloping  them  in  opposite  directions,  the  former  at 
a  grade  of  1  in  32,  and  the  latter  1  in  16.  If  such  dirt 
roads  are  not  provided,  then  turnouts  must  be  constructed  at 
intervals.  These  places  have  a  wooden  trackway,  16  ft.  in 
width,  with  the  planks  laid  on  4  instead  of  2  stringers,  to  which 
they  are  spiked. 

The  advantages  of  such  roads  are  that  they  reduce  the  trac- 
tive force  by  about  one-third  that  required  on  a  dirt  road,  and 
at  all  seasons  of  the  year  afford  a  good  highway. 

TRACKWAYS 

In  the  United  States  trackways,  whether  of  stone  or  steel, 
seem  to  be  less  popular  than  abroad,  for  in  a  number  of  towns  in 
northern  Italy  such  means  of  transporting  heavy  loads  is  quite 
common,  while  similar  roads  are  made  use  of  in  the  cities  of 
London,  Manchester,  and  Liverpool,  England.  In  Spain  a  steel 
trackway  2  miles  long  was  constructed  at  a  cost  of  $28,518  some 
years  ago,  about  1890,  which  seems  to  have  given  eminent  satis- 
faction. This  road,  joining  the  towns  of  Grao  and  Valencia,  had 
a  daily  traffic  of  3,200  vehicles,  and  yet  the  yearly  repairs  after 
7  years'  service  cost  but  $380,  while  previous  to  this  the  cost 
was  $5,470  per  annum. 

The  older  forms  of  trackway  consist  of  blocks  of  stone  varying 
in  dimensions,  but  usually  from  one  to  two  feet  wide,  placed  in 
lines  parallel  to  the  axis  of  the  road,  and  at  a  distance  apart 
equal  to  the  tread  of  the  wagon.  Between  these  lines  of  track 
a  cobble  or  broken-stone  pavement  is  laid  to  furnish  a  foothold 
for  the  horses,  and  with  this  combination  of  easy  traction  and 
good  foothold  the  hauling  of  very  heavy  loads  is  quite  possible. 
The  cost  of  such  wheelways  is  high,  but  frequently  they  are 
less  expensive  to  put  in  to  a  short  piece  of  road  on  a  steep  grade 


154  HIGHWAY   ENGINEERING 

to  reduce  the  tractive  force,  than  it  would  be  to  cut  down  the 
existing  grade  by  excavation.  At  less  than  half  the  cost  that 
would  have  been  needed  to  reduce  a  grade  from  1  in  20  to  1  in 
34,  Telford  on  the  Holyhead  road  produced  the  same  result  by 
introducing  stone  wheel  ways. 

A  cobble  or  stone  pavement  is  placed  for  some  distance  adja- 
cent to  the  tracks  to  give  them  a  solid  foundation  and  prevent 
too  great  wear  on  the  trackway  and  road  by  the  turning  on  or  off 
of  teams. 

Judson  in  his  book  on  "  City  Roads  and  Pavements  "  men- 
tions a  stone-block  trackway  that  was  built  on  the  Albany 
and  Schenectady  Turnpike  in  1833,  and  parts  of  which  are  still 
in  existence. 

"  The '  stone  rails '  were  made  4  ins.  thick  and  were  roughly  cut 
18  to  24  ins.  wide  of  any  length  from  2  to  8  ft.  with  square  ends  to 
be  laid  close  together  and  with  both  faces  flat  to  permit  of  turn- 
ing over  when  worn.  .  .  .  They  were  bedded  in  the  gravel 
and  broken  stone  of  the  roadway."  Between  the  track  and  on 
each  side  to  a  distance  of  5  ft.  was  a  cobble  pavement. 

In  1901  about  2,000  ft.  of  steel  double  trackway  was  laid  in 
Chicago,  111.,  but,  failing  to  give  satisfaction,  was  removed.  In 
1902  a  steel  wheel  way  designed  by  General.  Roy  Stone  of  the 
Office  of  Road  Inquiry  of  the  Department  of  Agriculture  was  laid 
in  Murray  Street,  New  York  City,  but  this,  too,  proved  unsatis- 
factory, as  horses  were  unable  to  secure  a  foothold.  It  has  since 
been  removed. 

SAND-CLAY   AND   BURNT-CLAY   ROADS 

Natural  sand-clay  roads  may  frequently  be  formed  in  localities 
where  the  soil  contains  the  right  proportions  of  sand  and  clay. 
Where  the  prevailing  subsoil  is  of  clay,  or  on  the  other  hand  of 
sand,  the  two,  if  properly  mixed,  may  succeed  in  overcoming  the 
objections  of  each.  This  is  particularly  important  to  the  At- 
lantic and  Gulf  States  where  these  materials  are  so  plentiful. 


MISCELLANEOUS   ROADS  155 

The  great  variation  in  the  physical  properties  of  clay  makes  it 
difficult  to  give  definite  rules  as  to  the  mixing. 

It  has  been  proven  that  such  roads  are  well  adapted  to  light 
traffic,  and  wear  well  under  heavy,  and  are  less  noisy,  dusty,  and 
expensive  than,  and  in  cases  preferable  to,  macadam. 

By  burning  the  clay  at  a  moderate  heat  it  loses  its  sticky 
quality,  and  becomes  able  to  bear  traffic  even  in  the  wettest 
weather. 

The  best  sand-clay  road  is  one  in  which  the  surface  is  com- 
posed of  grains  of  sand  in  which  the  voids  are  filled  with  clay 
that  acts  like  a  binder.  An  excess  of  clay  beyond  this  is  detri- 
mental. Where  this  condition  exists  for  a  few  inches  in  thickness 
upon  the  surface  of  a  road,  it  will  bear  comparatively  heavy 
traffic  for  a  long  time.  The  materials  should  be  mixed  thor- 
oughly while  wet  and  puddled  with  water.  This  is  easily  se- 
cured after  a  hard  or  long  rain,  the  clay  having  been  pre- 
viously spread  and  the  larger  lumps  broken  up. 


CHAPTER  VI 

STREET   DESIGN 

THE  object  sought  in  the  design  and  location  of  city  streets,  is 
a  symmetrical  arrangement  or  plan  by  which  an  easy  and  rapid 
means  of  intercommunication,  together  with  plenty  of  light  and 
air,  may  be  secured  at  a  minimum  cost  of  construction.  That 
many  of  the  European  cities  and  some  of  the  larger  ones  in  the 
United  States  have  failed  in  obtaining  such  results,  is  instanced 
by  the  notably  narrow  and  tortuous  streets  of  London,  Paris, 
Boston,  and  lower  New  York.  On  the  other  hand,  Berlin  is  an 
exception  to  the  general  conditions  in  Europe,  principally  be- 
cause of  its  enormous  development  practically  within  the  past 
fifty  years,  while  Washington,  D.  C.,  presents  probably  the  best 
design  that  is  to  be  found  on  this  side  of  the  Atlantic. 

Frequently  the  location  of  a  street  is  the  result  of  topograph- 
ical or  other  local  conditions,  which  may  neglect  the  considera- 
tions of  grade,  plan,  and  alignment.  But  with  the  growth  of  a 
community  some  intelligent  arrangement  must  be  adopted  to 
provide  for  the  present  and  future  needs  of  all  kinds  of  traffic,  and 
for  the  water,  sewerage,  and  lighting  systems  which  are  neces- 
sarily laid  beneath  the  surface  of  the  streets. 

LOCATION.  The  factors  governing  the  location  of  city  streets 
are  primarily  the  nature  of  the  topography  and  the  directness  of 
communication. 

Topography.  Located  with  regard  to  this  feature,  the  streets 
should  be  planned  to  secure  easy  grades  for  the  benefit  of  traffic 
and  should  furnish  satisfactory  slopes  for  surface  drainage,  as 
well  as  the  flow  of  water  or  sewage  in  the  conduits  placed  be- 
neath the  surface;  at  the  same  time  the  cost  of  construction 

156 


STREET   DESIGN  157 

should  be  a  minimum.  In  hilly  districts  alignment  is  a  second- 
ary, but  nevertheless  important  factor.  With  such  prevailing 
conditions,  the  object  to  be  attained  is  the  maintenance  of  the 
integrity  and  uniformity  of  the  plan,  yet  with  avenues  provided 
which  will  afford  easy  grades  for  the  traffic  and  drainage. 

Directness  of  Communication  can  be  the  controlling  feat- 
ure only  where  the  ground  is  level  or  approximately  so.  On  the 
other  hand,  where  the  land  is  particularly  flat  the  question  may 
be,  not  "  how  to  avoid  grade,"  but  rather  "how  may  grade  be 
secured."  With  the  obstacles  of  grade  eliminated,  a  harmonious 
plan  providing  the  shortest  and  easiest  lines  of  communication 
may  be  easily  adopted. 

Street  Plan.  Two  general  methods  in  the  arrangement  of 
city  streets  may  be  said  to  obtain:  1st,  the  rectangular  system; 
and  2d,  a  combination  of  the  rectangular  with  intersecting  diag- 
onals. 

THE  RECTANGULAR  SYSTEM  consists  of  parallel  lines  inter- 
sected by  other  parallel  lines  at  right  angles  to  the  former,  and 
has  the  advantage  of  giving  a  maximum  area  for  building  pur- 
poses which  may  easily  and  readily  be  subdivided  into  lots  of 
satisfactory  form.  It  is  the  much  more  common  method  of 
arranging  the  streets,  though  perhaps  not  quite  as  satisfactory  as 
the  other. 

In  this  system  the  avenues,  designed  for  business  purposes, 
should  be  parallel  to  each  other,  and  follow  the  lines  of  maximum 
traffic,  while  the  streets,  devoted  to  residences,  should  intersect 
these  at  right  angles.  Where  the  city  is  divided  into  business 
and  residential  sections,  the  blocks  should  be  square  to  admit  of 
speedy  intercourse;  but  where  the  two  exist  side  by  side,  the 
blocks  should  be  from  three  to  four  times  as  long  as  wide,  with 
the  residences  occupying  the  shorter  side  of  the  rectangle. 

New  York  City  is,  for  the  most  part,  an  example  of  the 
rectangular  system,  but  in  the  Borough  of  Manhattan,  where  the 
avenues  run  approximately  north  and  south,  and  the  streets  east 


158 


HIGHWAY  ENGINEERING 


and  west,  precisely  the  arrangement  that  should  have  been 
avoided  has  been  secured.  The  city  is  very  much  longer  on  a 
north  and  south  line  than  it  is  wide,  and  in  consequence,  and 
following  a  natural  law,  most  of  the  businesses  have  been  es- 
tablished on  the  avenues  while  the  side  streets  serve  for  the  resi- 


M 


\ 


} 


o 


// 


\ 


FIG.  53. — Arrangement  of  Streets. 


dences.  The  avenues,  therefore,  receive  the  bulk  of  all  kinds  of 
traffic — subsurface,  surface,  and  elevated — and  yet  instead  of  as 
many  avenues  as  possible  being  provided  to  accommodate  this 
traffic,  the  city  is  designed  with  the  avenues  from  two  to  three 
times  further  apart  than  the  streets,  thus  providing  three  times  as 


STREET   DESIGN  159 

many  thoroughfares  in  the  direction  where  the  requirements  are 
the  least,  i.e.,  east  and  west,  as  in  the  direction  where  they  are 
most. 

If  the  longer  sides  of  the  rectangles  were  north  and  south, 
it  would  further  aid  in  the  speed  of  transportation,  since  then  the 
surface-cars  at  least  would  be  required  to  stop  at  fewer  corners. 

Where  the  streets  are  numbered  as,  for  example,  1,  2,  3,  etc., 
the  house  numbers  should  in  a  similar  manner  agree  so  that  the 
street  number  may  indicate  the  location  of  the  house.  Thus  all 
house  numbers  between  100  and  200  might  be  found  between 
streets  10  and  20,  and  between  200  and  300  between  streets  20 
and  30,  etc. 

The  Diagonal  System  consists  of  the  rectangular,  together 
with  main  diagonal  thoroughfares  for  the  purpose  of  giving 
direct  lines  of  communication  from  one  centre  of  the  city  to 
another. 

It  further  provides  breathing  space  at  the  intersections,  which 
in  congested  districts  are  particularly  desirable,  affords  light  and 
air,  increases  the  valuation  of  property,  and  possesses  some 
aesthetic  qualifications.  While  the  principal  advantage  is  that  it 
saves  distance,  the  principal  disadvantage  is  that  it  consumes  too 
large  a  proportion  of  building  area.  The  advantages,  however, 
may  be  emphatically  said  to  outweigh  the  disadvantages,  as  in- 
creased valuation  due  to  frontage  more  than  counterbalances 
this;  Washington,  D.  C.,  is  the  most  notable  exponent  of  this 
system  of  street  design. 

The  following  is  an  abstract  taken  from  a  paper,  by  Lewis  M. 
Haupt,  which  shows  more  in  detail  the  advantages  of  the 
arrangement. 

"  The  systems  may  be  divided  into  two  classes:  1st,  regular, 
and  2d,  irregular.  The  first  class  may  be  subdivided  into  rec- 
tangular, diagonal,  and  circular;  the  second  into  every  possible 
kind  of  distortion  more  or  less  intricate,  according  to  the  circum- 
stances attending  the  growth  of  a  city.  The  latter  class  is  dis- 


160 


HIGHWAY   ENGINEERING 


carded  as  being  unscientific,  expensive,  inconvenient,  and  poorly 
adapted  to  the  requirements  of  a  growing  community. 

"  As  people  move  through  a  city  in  every  conceivable  direc- 
tion, it  will  be  impossible  to  provide  the  shortest  lines  for  all; 
but  the  case  may  be  met  by  supposing  a  greater  or  less  number  of 
centres  or  points  d'appui,  to  and  from  which  the  currents  of  daily 
life  flow  and  ebb. 

"  With  reference  to  the  subdivision  of  the  first  class,  it  is 
evident  that,  the  straight  line  being  the  shortest  distance  between 
two  points,  the  chord  will  be  shorter  than  its  arc,  and  hence  the 


JL 


L       J 


L 


Area 


W 


r     n 

FIG.  54. 


circular  system  is  defective.  The  rectangular  compels  a  waste  of 
distance  and  time,  and  the  diagonal  by  itself  becomes  the  rec- 
tangular, so  that  no  single  system  fulfils  all  possible  requirements. 
A  combination  must,  therefore,  be  resorted  to,  and  that  composed 
of  right-line  elements  is  both  the  simplest  and  most  direct.  A 
judicious  arrangement  of  diagonal  streets  with  the  rectangular 
system  will  doubtless  be  found  to  meet  more  fully  than  any  other 
the  requirements  of  the  case;  but  it  is  evident  that  if  the  streets 
be  too  wide  or  too  numerous,  the  building  areas  will  be  corre- 
spondingly decreased  and  a  certain  proportion  of  people  forced 
beyond  given  limits,  thus  increasing  their  distances.  On  the  other 
hand,  the  diagonals  will  in  general  open  new  building  lines  with 


STREET  DESIGN  161 

more  than  residences  enough  to  provide  for  all  the  displaced  in- 
habitants. 

"  To  illustrate  the  utility  of  such  a  combination,  suppose  a 
portion  of  a  town  or  city  to  be  laid  out  in  the  form  of  a  square 
whose  side  is  L  feet  long,  and  in  which  the  blocks  are  I  feet  square 
and  the  streets  w  feet  wide. 

"  Let  the  diagonals  of  the  large  square  be  opened  as  thorough- 
fares, and  note  their  effect.  The  blocks  or  small  squares  extend 
from  the  middle  of  one  street  to  that  of  its  parallel,  or  from  the 
building  line  of  one  block  to  that  of  the  next  ;  hence  the  length  of 
a  side  of  such  a  square  must  be  I  +  w  (Fig.  54)  . 

"  The  area  of  the  small  square,  including  the  streets,  multi- 
plied by  the  number  of  such  squares,  will  give  the  area  L2  of 
that  portion  of  the  city,  and  the  ratio  of  street  to  property  area  is 
the  same  for  the  small  as  for  the  large  squares  ;  but  the  area  of 
the  small  squares  is  (I  +  w)2  =P  +  2lw  +  v?,  in  which  Z2  is  the 
property  or  building  area,  and  2lw  +  w2  is  the  street  area;  the 

ratio  being  —  and  the  percentage  of  street  to  property 

i 

area, 

.(A) 


"  For  any  rectangle  with  streets  of  unequal  widths,  the  gen- 
eral formula  would  be 


ac 


in  which  a  and  c  are  the  sides  of  the  rectangle,  and  b  and  d  the 
widths  of  the  streets.  If  these  quantities  are  equal,  each  to  each 
(A1)  becomes  (A).  The  number  (ri)  of  blocks  in  a  given  square 
whose  area  is  L2  will  be 


"  If  now  two  diagonals,  MN  and  PQ  be  introduced,  it  is  evi- 
11 


162  HIGHWAY   ENGINEERING 

dent  that  where  they  cross  the  rectangular  streets  no  additional 
area  is  taken  from  the  private  property  of  the  city,  but  they 
will  cut  out  of  each  of  the  small  squares  which  they  cross  an 

_  -JM 

area  whose  length  is  >/2P  —  -~-,  breadth  w,  and  whose  area  for 


one  block,  P,  isf\/2Z2  —  ~^)w  (see  Fig.  54).  For  n  blocks  the 
total  building  area  consumed  from  L2  by  both  diagonals  when 
n  is  even  will  be  2nw(\/2P  -  -=-),  and  the  percentage  of  the 

building  area  will  be  -—  -(\/2P—  -—  )  X  100,  which  reduces  to 

n    i        \  £    / 


(C) 


the  formula  for  diagonals  when  n  is  even.     If  n  be  odd,  C  becomes 
-^(2.8280100  =  282.8  ^  ............  (C1) 

"  If  diagonals  be  opened,  benefits  will  accrue  both  from  the 
shortening  of  distance  and  the  additional  frontage  which  will  be 
furnished,  while  but  a  small  proportion  of  the  inhabitants  will  be 
displaced.  The  greatest  economy  in  distance  will  be  in  passing 
from  M  to  0  (Fig.  53),  which  by  the  square  system  is  equal  to  L, 

and  by  the  diagonal  L  VT£  the  ratio  being  L  L4142 


—  , 
Li  2          100 

the  numerator  indicating  the  distance  (in  feet)  by  the  diagonals, 
the  denominator  by  the  squares.  This  gives  a  gain  of  30  per 
cent,  which  is  the  greatest  amount  possible  and  from  which  it 
diminishes  to  zero  at  P. 

"  The  total  length  of  frontage  on  the  streets  in  the  square 
system  is  4Zn2.  The  diagonals  give  an  additional  length  of 
4n(\/2l2  —  w),  and  the  percentage  of  increase  is  therefore 

..(D) 


STREET  DESIGN 

L i  LJLJLJ 


163 


nnnnn 

DDDDD 

nnDnn 


DDDD 

nnnn 

DDDD 

nnnn 


nnnn 


164  HIGHWAY   ENGINEERING 

"  The  ratio  of  people  displaced  is  the  same  as  that  of  the  area 
consumed  by  diagonals  to  the  entire  area  L2. 

"  To  determine  these  values  for  any  particular  case,  and  so 
discover  whether  or  not  the  diagonals  will  be  beneficial,  let  /  =  500 
ft.,u>  =  50  ft.,  and n  =  10. 

"  Formula  (A)  gives  21  as  the  percentage  of  large  or  small 
squares  consumed  by  streets  in  the  rectangular  system. 

"  Formula  (C)  gives  only  2.82  per  cent  of  additional  building 
area  consumed  by  diagonals. 

"  Formula  (D)  gives  13  per  cent  as  the  increase  in  frontage 
due  to  diagonals,  and  it  has  been  shown  that  the  saving  of  dis- 
tance varies  from  30  per  cent  to  nothing. 

"  The  number  of  people  displaced,  which  is  only  2.82  per  cent, 
will  be  abundantly  provided  for  by  the  additional  frontage  on  the 
diagonals,  revenues  will  be  augmented  by  assessments  on  the  new 
buildings  erected,  and  a  large  saving  will  be  effected  in  time  and 
distance  for  a  majority  of  the  inhabitants  by  this  combination  of 
systems,  which  is  therefore  found  to  fulfil  the  requirements  of 
practice  more  fully  than  any  other. 

"  Similar  applications  of  the  above  formula  will  show  to  what 
extent  the  plans  of  cities  already  established  or  to  be  built,  may 
be  improved  by  the  opening  of  diagonals;  the  most  economical 
relation  of  street  to  building  area,  the  proper  distribution  of  the 
street  area,  and,  by  extending  the  analysis,  the  ratio  of  pavement 
to  carriageway  may  also  be  readily  determined.  All  of  these 
questions  have  a  direct  bearing  on  the  convenience,  health,  and 
extension  of  our  cities." 

Fig.  55  shows  the  system  adopted  in  laying  out  the  streets 
of  Washington,  D.  C. 

Size  of  Blocks.  In  the  rectangular  system  the  blocks  are  in 
the  form  of  a  parallelogram,  and  where  there  is  a  preponderance 
of  traffic  in  one  direction  it  would  seem  to  be  the  most  satisfactory 
arrangement.  They  should  be  rather  long  and  narrow,  i.e.,  with 
the  length  from  3  to  4  times  the  width,  the  latter  being  about  200 


STREET   DESIGN  165 

ft.  This  limiting  width  is  determined  by  the  depth  of  2  lots,  since 
it  is  undesirable  and  prohibited  to  have  buildings  so  situated  as 
to  lack  street  frontage.  A  depth  of  200  ft.  permits  of  plenty  of 
light  and  air  in  the  rear  of  buildings,  while  a  length  of  600  to 
800  ft.  will  provide  sufficient  cross  streets  to  make  all  houses 
easily  accessible.  Probably  the  best  arrangement  of  the  houses 
in  the  rectangular  system  is  with  a  main  alley  at  the  rear,  about 
twenty  feet  wide,  i.e.,  wide  enough  to  permit  of  two  teams  passing, 
centrally  located  and  running  the  long  way  of  the  block.  Suf- 
ficient alleys  should  connect  with  the  side  streets  to  insure  ready 
entrance  to  the  main  one.  This  design  permits  of  the  trades- 
people entering  from  the  rear,  and  avoids  the  unsightly  and  dis- 
agreeable conditions  that  arise  when  house  refuse,  garbage,  etc., 
must  be  collected  from  in  front  of  one's  main  entrance. 

Size  of  Lots.  Lots  25  X  100  ft.  are  well  suited  to  both 
business  and  residential  needs.  In  New  York  City,  however, 
where  the  values  of  real  estate  are  so  high,  the  frontage  has  been 
decreased  in  many  cases  to  20  ft.  or  less. 

The  depth  is  determined  by  the  distance  between  streets,  as 
no  houses  are  permitted  to  be  built  unless  facing  on  a  thorough- 
fare. This  prevents  the  unhealthy  and  unsanitary  conditions 
that  exist  with  "  rear  tenements,"  and  insures  light  and  air  to  the 
occupants  of  houses.  To  further  provide  for  both  of  these 
there  is  an  ordinance  in  the  city  of  New  York  which  allows  only 
a  certain  percentage  of  any  lot  to  be  built  upon. 

In  residential  districts,  particularly  in  small  towns,  where  ap- 
pearance and  health  are  more  carefully  considered,  the  houses 
may  be  placed  in  the  centre  of  two  or  more  lots,  thus  securing 
breathing  space,  and  adding  to  the  looks.  On  the  other  hand,  in 
business  sections,  within  limits,  it  is  highly  desirable  to  have  the 
buildings  as  close  together  as  possible,  not  only  to  concentrate, 
but  to  promote  trade. 

Width  of  Carriageway  depends  upon  the  kind  and  amount 
of  traffic,  which  in  turn  is  related  to  the  nature  of  the  district  in 


166  HIGHWAY   ENGINEERING 

which  the  street  is  located.  Residential  streets  should  be  from 
thirty  to  eighty  feet  between  curbs,  specific  values  depending 
upon  local  conditions.  In  foreign  cities  usually  some  percentage  of 
the  width  of  street  is  taken.  The  smaller  values  seem  to  be 
much  more  prevalent  in  the  East,  while  the  general  practice  in 
the  West  tends  toward  the  larger  values.  The  above  widths  will 
ordinarily  provide  enough  space  for  carriage  or  light  delivery 
traffic,  and  at  the  same  time  afford  sufficient  light  and  air  to  as- 
sure a  healthful  condition.  The  latter,  i.e.,  the  light  and  air, 
are  beginning  to  be  appreciated  as  important  factors  with  the 
present  pronounced  tendency  toward  " skyscrapers, "particularly 
in  large  cities.  In  view  of  these  facts  a  height  limit  for  buildings 
at  Springfield,  Mass.,  has  been  proposed  the  object  of  which  is  to 
limit  the  height  of  all  buildings  to  100  ft.  in  the  business  section 
and  80  ft.  in  residential,  and  also  to  preclude  buildings  being 
erected  that  are  higher  than  1J  times  the  width  of  street.  The 
reasons  for  these  limitations  are  purely  sanitary. 

On  business  streets  the  distances  between  curbs  vary  from 
80  to  140  feet.  Such  widths  are  necessary  to  provide  against 
the  congestion  of  traffic,  and  to  permit  of  the  operation  of  street- 
car lines.  The  above  figures  are  seldom  exceeded,  though  fre- 
quently the  values  in  practice  fall  short  of  them.  Thus  in 
Brooklyn,  N.  Y.,  there  are  streets  only  thirty-four  feet  wide  which 
contain  two  trolley-car  tracks.  Where  surface  lines  exist  it  is 
better  to  have  the  streets  wider  than  under  normal  conditions, 
and  some  advantage  will  be  found  in  placing  the  tracks  at  one 
side  of  the  street  rather  than  in  the  centre. 

Width  of  Pavement  depends  upon  practically  the  same  fac- 
tors as  width  of  carriageway.  In  residential  districts  the  width 
of  paved  foot  walks  may  be  eight  feet  as  a  minimum,  with  the  rest 
of  the  sidewalks  sodded  with  grass  and  planted  with  shade-trees. 
Greater  width  is  probably  not  needed,  except  under  peculiar  con- 
ditions, and  the  increased  width  only  adds  to  the  expense  of  con- 
struction, maintenance,  and  repair.  In  large  cities  and  in  the 


STREET   DESIGN  167 

business  districts  the  entire  space  between  building  line  and  curb 
should  be  paved,  and  this  width  should  have  values  between 
twenty  and  thirty  feet. 

Street  Grades.  The  grade  of  a  street  is  very  important,  as 
upon  it  depends  the  surface  drainage,  which  is  a  factor  in  the 
health  of  the  community,  the  grade  of  the  water  and  sewer  pipes 
beneath  the  surface  of  the  street,  and  the  load  that  may  be 
hauled  over  the  pavement.  Such  grades  should  as  a  rule  be 
established  before  improvements  are  begun,  as  they  are  very 
much  more  economically  located.  "  No  arbitrary  rule  for  a 
maximum  grade  can  be  laid  down.  But  in  a  city  that  has  been 
partially  improved  no  grade  should  be  established  in  excess  of 
the  maximum  at  that  time  in  force,  unless  absolutely  necessary." 
While,  under  ordinary  conditions,  the  grade  should  be  as  small  as 
possible,  in  Chicago  the  extreme  case  presents  itself,  for  the  city 
is  so  flat  that  it  becomes  a  problem  to  secure  drainage. 

A  grade  of  eight  or  ten  per  cent  ought  to  be  the  maximum, 
though  grades  greatly  in  excess  of  this  exist  in  many  of  our  larger 
cities  and  are  frequently  used.  Such  values  do  not,  of  course, 
present  the  same  difficulties  to  light  pleasure  traffic  as  to  heavy 
trucking,  but  for  the  latter,  ten  per  cent  may  be  said  to  be  the 
maximum.  Beyond  this  it  will  be  difficult  and  expensive  to 
haul,  particularly  under  unfavorable  atmospheric  conditions, 
despite  the  fact  that  for  short  distances  horses  are  enabled  to 
exert  approximately  twice  their  normal  effort.  In  Duluth, 
Minn.,  a  particularly  hilly  city,  grades  of  12  per  cent  are  found; 
hi  Pittsburg,  Pa.,  the  maximum  is  17  per  cent;  and  in  New 
York  18  per  cent. 

On  such  heavy  grades  the  foothold  should  be  as  nearly  perfect 
as  possible,  while  the  pavement  should  at  the  same  time  offer 
as  little  resistance  to  the  vehicles.  No  such  pavement  com- 
bines these  two  characteristics  to  a  marked  degree,  and  in  con- 
sequence foothold  takes  precedent  over  smoothness  of  surface. 
For  this  reason  brick,  cobble,  or  granite  block  should  be  used  on 


168  HIGHWAY   ENGINEERING 

steep  grades,  though  on  inclines  of  5,  6,  and  7  per  cent  asphalt 
seems  to  be  chosen  by  drivers  in  preference  to  the  rougher 
pavements. 

The  more  important  factors  influencing  the  choice  of  grade 
are  drainage,  both  surface  and  underground,  cost  of  construction, 
consideration  of  traffic,  and  the  effect  on  the  value  of  abutting 
property. 

Grades  at  Street  Intersections.  The  establishment  of 
grades  at  street  intersections  more  often  requires  the  use  of  judg- 
ment and  ingenuity  than  the  following  of  some  rule  of  thumb. 
The  plan  adopted  by  Herring  and  Rosewater,  however,  in  the 
setting  of  grades  at  intersections  in  the  streets  of  Duluth,  Minn., 
is  frequently  quoted,  and  is  perhaps  as  satisfactory  a  method  as 
has  been  so  far  suggested. 

At  intersections,  in  the  business  sections,  grades  are  flattened 
to  three  per  cent  for  the  width  of  the  roadway  of  the  intersecting 
streets,  and  that  of  the  curb  is  flattened  to  eight  per  cent  for  the 
width  of  the  intersecting  sidewalks.  Grades  of  less  amounts, 
on  roadway  or  sidewalk,  are  continuous.  The  elevation  of  prop- 
erty corners  is  found  by  adding  together  the  curb  elevation  at 
the  points  facing  the  property  corners  and  also  the  sum  of  the 
widths  of  the  2  sidewalks  of  the  corners  multiplied  by  2J  per  cent, 
and  dividing  the  whole  by  2.  This  gives  an  elevation  equal  to 
the  average  elevation  of  the  curbs  opposite  the  corner,  and  an 
average  rise  of  2J  per  cent  across  the  width  of  the  sidewalk. 

Another  method  of  adjusting  grades  at  street  intersections  is 
to  give  the  4  building  corners,  the  4  curb  corners,  and  the  8  points 
on  the  curbs  opposite  the  building  corners  all  the  same  elevation. 
This  arrangement  is  satisfactory  only  when  the  grade  is  small,  i.e., 
under  3  per  cent. 

The  most  usual  method  of  establishing  grade  at  intersections 
is  by  considering  the  grades  of  the  centre  lines  alone,  but  this, 
especially  on  side  hill  streets,  leads  to  confusing  and  unsatisfac- 
tory results. 


STREET   DESIGN  169 

Side  Hill  Streets  present  some  difficulties  at  corners  and 
crossings  where  the  grade  is  at  all  excessive.  With  normal  con- 
ditions, a  street  will  be  located  symmetrically  with  regard  to  a 
longitudinal  centre  line,  and  the  same  grades,  etc.,  will  obtain 
on  one  side  as  on  the  other ;  but  where  transverse  grades  exist, 
other  arrangements  will  have  to  be  made  in  determining  the 
elevation  of  building  corners,  slope  of  pavement,  elevation  of 
curb  corners,  transverse  grade,  position  of  crown,  depth  of  gutter, 
height  of  curb,  etc.,  etc.  Under  all  circumstances  a  grade  of 
J  in.  to  f  in.  per  ft.  should  be  given  the  sidewalk  to  secure 
drainage,  and  the  height  of  curb  should  have  a  minimum  value  of 
3  ins.  and  a  maximum  of  10  ins.  To  accommodate  the  street, 
then,  to  the  grades,  carefully  exercised  judgment  will  have  to  be 
used. 

It  is  the  general  practice  where  the  transverse  grade  is  some- 
what small,  to  swing  or  throw  the  centre  of  the  crown  toward  the 
high  side  of  the  street,  to  make  the  height  of  curb  on  opposite 
sides  of  the  street  unequal,  or  provide  different  grades  for  the 
sidewalks;  but  where  the  grade  is  large,  .the  whole  street  may 
have  to  slope  transversely  with  the  grade,  and  under  extreme 
conditions  the  higher  side  will  have  to  be  terraced. 

STREET   DRAINAGE 

Drainage  of  streets  may  be  divided  into  two  classes :  surface, 
and  subsurface. 

Surface  Drainage  is  for  the  purpose  of  collecting  in  the  gutters 
all  water  falling  either  upon  the  foot-  or  the  carriageway,  and  so 
directing  it  that  it  may  be  discharged  into  a  catch-basin,  sewer,  or 
some  natural  outlet.  To  care  for  the  water  falling  on  the  foot- 
way, a  grade  of  one-eighth  inch  per  foot  should  be  given,  away 
from  the  house-line  toward  the  gutter ;  this  will  insure  the  water 
flowing  into  the  latter  while  the  water  falling  on  the  carriageway 
will  be  directed  toward  the  same  gutter  by  means  of  the  crown. 

Gutters  should  be  deep  enough  to  carry  off  the  maximum 


170  HIGHWAY   ENGINEERING 

amount  of  storm  waters.  They  are  formed  of  the  same  material 
as  the  roadway  itself  where  that  is  asphalt,  wood,  granite  block, 
etc.,  but  on  streets  where  gravel  or  macadam  are  used,  cobble  or 
blocks  of  stone  will  have  to  be  employed  to  avoid  the  scouring 
action  of  the  storm  waters.  Asphalt,  when  subjected  to  the  con- 
tinued action  of  water,  rots,  and  to  prevent  this  disintegration  by 
the  storm  waters  in  the  gutters,  a  coating  of  pure  bitumen  is 
painted  along  a  narrow  strip  next  the  curb  where  the  storm 
waters  flow.  On  the  very  superior  gravel  and  broken-stone  roads 
of  Central  Park,  New  York  City,  the  gutters  are  formed  of  a 
shallow  trough  about  fifteen  inches  wide  and  four  inches  deep, 
which  drain  into  catch-basins  placed  in  the  path  of  the  gutters. 

Where  the  streets  possess  curbs,  the  gutters  are  usually  formed 
by  the  vertical  face  of  the  curbstone  and  the  pavement  adjacent 
to  it,  but  on  the  streets  of  country  towns  the  gutter  is  often  placed 
some  distance  from  the  walk,  where  perhaps  no  curb  exists,  and  it 
is  then  formed  by  paving  the  bottom  of  a  trench  with  small-sized 
stone  to  prevent  erosion.  The  depth  of  the  gutter  should  be  from 
three  inches  to  ten  inches,  and  should  be  uniform  on  streets  with 
any  grade,  though  on  level,  or  approximately  level,  streets  the 
depth  of  the  gutter  will  vary  so  that  proper  drainage  may  be 
effected. 

The  grade  of  the  gutter  in  all  ordinary  cases  depends  upon 
the  longitudinal  grade  of  the  street,  but  a  slope  of  1  in  100  at 
least  ought  to  be  provided  to  secure  satisfactory  drainage. 

Curb.  The  curb  serves  the  double  purpose  of  holding  both 
the  sidewalk  and  pavement  of  the  carriageway  in  place,  and  at 
the  same  time  acting  as  a  sort  of  shoulder  for  the  gutter  to  con- 
fine the  storm  waters  there  that  are  directed  to  the  sides  by 
means  of  the  crown.  Generally  speaking,  curbs  should  not  be 
higher  than  ten  inches  nor  less  than  three  inches,  as  the  former 
make  them  difficult  to  step  up  to,  and  the  latter  will  be  too  shal- 
low to  prevent  the  water  from  flowing  over  the  walk.  Curbs  are 
usually  formed  of  slabs  of  stone  about  6  ins.  thick,  18  ins.  to  24 


STREET   DESIGN 


171 


ins.  deep,  and  varying  in  length;  but  they  are  often  made  of 
concrete,  especially  when  formed  in  combination  with  the  gutter. 
A  stone  that  will  resist  the  action  of  traffic,  i.e.,  wheels  scraping 
along  the  front  face,  and  one  that  is  non-absorbent,  is  best  suited 
to  the  purpose,  as  it  will  thus  better  resist  the  weather  action. 
For  this  reason,  granite,  limestone,  bluestone,  and  sandstone  are 
frequently  used.  All  exposed  faces  and  joints  are  usually  dressed 
so  as  to  secure  a  close,  even  contact,  and  present  a  pleasing 
appearance. 

The  face  next  the  gutter  is  inclined  away  from  the  vertical 


|®|i|^6£Sii 


FIG.  56. — Concrete  Curb  and  Gutter. 

to  prevent  the  wheels  from  too  readily  breaking  or  chipping  the 
curb  when  wagons  are  backed  up  against  it,  while  the  horizontal 
face  is  given  the  same  slope  as  the  sidewalk  for  drainage. 

At  corners  the  curb  should  be  curved,  the  minimum  radius 
being  about  2  ft.  and  the  maximum  about  12  ft.;  the  more  usual 
values,  however,  lie  between  6  and  12  ft.  Too  large  a  radius  is 
expensive  and  not  so  convenient  for  people  crossing  the  streets. 

The  above  cut  shows  the  design  of  a  concrete  gutter  and  curb. 

"  The  most  obvious  thing  about  it  is  the  curved  waterway 
in  the  form  of  a  segment  of  a  circle  with  its  chord  inclined  at  the 


172  HIGHWAY   ENGINEERING 

same  slope  as  the  last  quarter  of  the  street  and  the  first  6  ins.  of 
the  gutter.  This  slope  is  f  in.  to  1  ft.  This  plane  lip  practically 
continues  the  roadway  and  makes  it  possible  to  secure  a  smooth 
joint  with  the  pavement,  and  thus  allows  the  water  to  run  freely 
into  the  gutter,  which  is  the  main  feature  of  the  design.  This 
segment  has  about  a  12  in.  chord  and  a  3  in.  rise,  making  its  area 
25.2  sq.  ins.  or  about  that  of  a  6  in.  pipe  (28.2  sq.  ins.).  It  is 
evident  that  there  is  a  chance  for  a  large  amount  of  water  to  run 
before  the  triangular  space  between  the  chord  and  the  level  line 
from  the  edge  of  the  gutter  is  filled.  This  latter  space  represents 
the  ordinary  gutter  of  one  plane. 

"  The  advantages  of  a  combined  concrete  curb  and  gutter  of 
this  type  in  the  way  of  looks,  efficiency,  and  cost  are  so  great 
that  it  seems  the  obvious  thing  wherever  a  good  concrete  stone  is 
available  at  a  reasonable  price." 

Crown.  The  crown  on  city  streets  as  upon  country  roads 
consists  either  of  two  intersecting  planes  or  of  a  curved  profile. 
Curves  are  the  much  more  usual  form  and  are  either  circular  or 
parabolic.  They  have  the  advantage  of  giving  a  flat  profile 
in  the  centre,  where  the  most  traffic  is,  and  where  it  is  most 
desirable  that  it  should  be  level,  besides  giving  deep  shoulders 
or  gutters,  thus  reducing  the  area  that  must  be  devoted  to 
such  purposes. 

»  The  crown  is  naturally  for  the  purpose  of  directing  the  surface 
waters  toward  the  gutters,  and  the  smoother  the  pavement 
the  less  it  should  be.  But  it  should  be  stated  that  while  asphalt 
is  the  smoothest  pavement,  and  should  therefore  receive  the  least 
crown,  in  some  cities  it  is  the  practice  to  give  it  the  maximum 
value.  This  is  because  the  foundation,  however  well  built,  will 
give  to  a  slight  extent  under  normal  traffic  conditions,  and  the 
asphalt,  with  no  support  and  possessing  no  structural  rigidity 
in  itself,  fails  to  stand  up  under  the  imposed  loads.  Depressions 
form,  in  which  rain  collects  and  rots  the  asphalt. 

For  asphalt,  sheet  or  block,  brick,  or  wood,  the  crown  will  be 


STREET  DESIGN  173 

about  the  same  and  vary  from  1  in  50,  as  a  minimum,  to  1  in  20, 
as  a  maximum.  Macadam  will  vary  from  1  in  24  to  1  in  12,  and 
granite  blocks  will  have  a  crown  of  about  1  in  30.  Such  values 
will,  of  course,  be  modified  to  some  extent  on  side  hill  streets  to 
better  accomplish  the  required  results  under  the  peculiar  existing 
conditions. 

Longitudinal  Grade.  The  longitudinal  grade  should,  for 
efficient  drainage,  be  about  1  per  cent,  though  in  cases,  as  small  a 
grade  as  1  in  300  has  successfully  disposed  of  the  surface  drainage. 
Whatever  the  grade  of  the  axis  of  the  street  is,  it  will,  within 
small  limits,  determine  the  grade  of  the  gutter. 

Drainage  at  Street  Intersections  requires  care  and  judgment, 
for  usually  the  most  traffic  of  vehicles  and  pedestrians  occurs  at 
these  points.  It  is  the  general  practice,  or  at  least  the  more 
common  one,  to  place  the  catch-basins  at  the  corners,  and  hence 
the  greatest  volume  of  water  occurs  at  these  points.  Unless  the 
gutters  are  unusually  wide  and  deep,  thus  making  it  not  only 
difficult  crossing  for  pedestrians,  but  also  turning  the  corners  for 
vehicles,  the  water,  in  times  of  heavy  rains,  will  tend  to  cover 
the  footwalk,  and  in  cold  weather  the  catch-basins'  mouth  may 
be  easily  clogged,  leaving  a  miniature  lake  for  people  to  wade 
around  or  through. 

If,  on  the  other  hand,  the  gutter  is  carried  under  the  cross- 
ing stones,  then  the  possibilities  of  it  becoming  choked  are  corre- 
spondingly great. 

To  obviate  this  condition  with  the  consequent  inconvenience 
to  pedestrians,  the  catch-basins  should  be  placed  in  the  gutter 
some  distance  from  the  corner. 

Subsurface  Drainage.  It  is  just  as  important  that  the  sub- 
surface of  a  city  street  be  well  drained,  to  support  the  overlying 
pavement,  as  of  country  roads.  This  may  be  accomplished  by 
porous  tile  pipe  with  closed  joints  being  placed  under  each  gutter, 
and  draining  into  the  catch-basins. 

Catch-basins  are  simply  vaults  arranged  conveniently  to 


174  HIGHWAY   ENGINEERING 

receive  the  surface  drainage,  and  for  the  purpose  of  collecting 
debris,  paper,  sand,  stone,  sticks,  etc.,  carried  along  with  the 
water,  that  it  may  settle  there  instead  of  flowing  through  other 
conduits  with  the  possibility  of  clogging  them.  These  catch- 
basins  are  placed  below  the  surface  of  the  ground,  the  mouth 
being  protected  by  iron  bars  or  screens  so  as  to  readily  admit 
the  water  and  yet  prevent  larger  solids  from  entering.  Periodic- 
ally they  are  cleaned  out  and  are  better  when  they  will  admit  a 
man's  body  for  the  purpose. 

TREES 

Apart  from  the  aesthetic  side  of  the  question,  trees  furnish 
shade,  temper  the  atmosphere,  absorb  water  from  the  roadbed, 
and  act  as  a  shield  against  snow  and  wind.  The  financial  aspect 
should  be  considered  also,  as  well-placed  shade-trees  increase  the 
valuation  of  property.  On  the  other  hand,  producing  shade  and 
acting  as  a  wind-break  to  the  road,  trees  prevent  the  very  de- 
sirable wind  and  sun  action  which  are  so  important  and  effective 
in  drying  out  the  soil. 

But  whatever  the  disadvantages  of  trees  may  be,  it  is  and 
has  been  the  practice  in  the  most  progressive  road-building  coun- 
tries to  plant  them  systematically  along  the  highways  and  more 
particularly  along  suburban  residential  streets. 

In  France  all  roads  having  a  width  of  32.8  ft.  and  over,  have 
a  single  row  of  trees  on  each  side,  the  trees  being  placed  at  a  dis- 
tance of  16.4  ft.  to  32.8  ft.  apart  and  on  wider  roads  double  rows 
are  established.  In  some  countries  fruit-trees  are  planted  from 
which  the  government  receives  a  revenue  by  the  sale  of  the  privi- 
lege to  pick  the  fruit. 

The  kind  of  tree  to  be  used  depends  principally  upon  the  local 
conditions,  i.e.,  climate,  environment,  soil,  air,  space,  etc.,  but 
one  should  be  selected  that  is  not  easily  affected  by  long  dry  or 
wet  spells,  dust,  heat,  smoke,  foul  air,  soot,  insects,  injury,  etc., 


STREET   DESIGN  175 

etc.  They  should  provide  plenty  of  foliage,  be  rapid  in  growth, 
yet  long-lived  and  pleasing  in  form. 

The  trees  are  usually  placed  from  twenty-five  to  fifty  feet 
apart  so  that  their  limbs  may  not  interfere,  and  where  there  is  a 
pavement  the  entire  width  of  the  walk,  are  protected  by  an  iron  or 
stone  grating  around  the  base  of  the  trunk. 

In  Massachusetts,  where  during  the  past  few  years  tree  plant- 
ing  along  the  public  highways  has  received  some  attention,  the 
following  varieties  were  planted  in  1905,  showing  the  variety  and 
choice  of  selection:  1,737  maples: — sugar,  Norway,  white;  1,000 
elms;  538  oaks: — red,  scarlet,  white,  pin;  and  some  six  hundred 
of  various  kinds,  including  the  white  pine,  locust,  willow,  etc. 
The  cost  of  these  trees  in  1905  was  $1.14  each,  and  in  1906  $1.01. 

According  to  the  Commission,  the  destruction  of  the  trees 
results  from  small  boys,  careless  drivers,  stray  cattle,  drought, 
and  insects. 


CHAPTER  VII 
STONE  PAVEMENTS 

COBBLESTONE.  While  it  is  a  fact  that  cobblestone  pavements 
are  seldom,  if  ever,  laid  to-day  except  where  the  grade  or  the 
traffic  is  heavy,  mention  must  be  made  of  them  because  of  their 
extensive  and  almost  exclusive  use  during  the  period  when 
pavements  were  first  being  laid  in  American  cities. 

A  COBBLESTONE  PAVEMENT  is  one  consisting  of  rounded  stones 
placed  upon  a  suitably  prepared  foundation  of  either  the  natural 
soil  or  sand.  Originally,  most  of  the  pavements  in  the  United 
States  were  constructed  of  this  material  because  of  the  advan- 
tages they  presented  in  the  cheapness,  accessibility,  and  durability 
of  the  stone,  though  their  many  disadvantages  have  been  the 
means  of  other  pavements  being  substituted  for  them.  A 
cobblestone  is  any  well-rounded,  water-worn  stone,  taken  from 
beaches  or  gravel  pits,  and,  as  used  in  pavements,  about  the 
shape  of  an  egg,  though  much  larger.  For  paving  purposes  the 
stone  should  never  be  less  than  4  ins.  in  diameter  nor  greater  than 
8  ins.,  and  from  5  ins.  to  10  ins.  deep.  The  stone  may  be  laid 
upon  the  natural  soil,  though  this  is  hardly  satisfactory,  or  upon 
a  foundation  of  loamy  sand  of  about  6  ins.  in  depth.  If  a  greater 
depth  of  sand  is  used,  or  if  the  sand  is  too  clean,  it  is  found  that 
the  cobbles  have  a  tendency  to  overturn  under  the  action  of 
traffic.  The  stones  are  set  on  end,  that  is,  with  the  long  dimen- 
sion vertical  and  rammed  into  place  by  a  50  Ib.  rammer,  while 
over  the  surface  is  spread  a  2  in.  layer  of  sand  or  gravel  for  the 
purpose  of  filling  the  joints  and  aiding  in  holding  the  stones  in 
place. 

176 


STONE   PAVEMENTS  177 

There  are  few  advantages  and  many  disadvantages  connected 
with  a  cobblestone  pavement.  It  is  cheap  and  furnishes  an 
excellent  foothold  for  horses;  but,  on  the  other  hand,  it  is  rough, 
noisy,  pervious,  requires  a  maximum  of  tractive  force,  has  a 
poor  bond  at  joints,  is  easily  rutted,  hard  to  keep  clean,  unsani- 
tary, and  in  fact  may  be  said  "never  to  give  satisfaction,  being 
only  a  substitute  for  a  pavement." 

Cobblestones  may,  however,  be  used  to  advantage  where 
heavy  loads  are  to  be  hauled  on  trackways,  over  which  the  wheels 
run,  and  between  which  the  rounded  stones  are  laid  to  offer  a 
foothold  to  the  horses. 

This  applies  more  particularly  to  one-horse  loads,  or  where 
two  or  more  are  hitched  ahead  of  each  other,  as  is  the  custom 
to  a  considerable  degree  in  Europe,  for  where  the  horses  are  har- 
nessed two  abreast,  as  in  America,  so  that  they  walk  in  the 
tread  of  the  wagon,  i.e.,  on  the  track  ways,  no  advantage  is  to  be 
gained. 

BELGIAN   BLOCK 

This  pavement  superseded  the  "  barbarous"  cobblestone  be- 
cause of  its  superiority,  though  it  in  turn  has  been  discarded  in 
favor  of  the  granite-block,  or  block-stone  pavement  for  a  like 
reason,  where  the  demands  of  traffic  have  been  such  as  to  require 
a  covering  of  this  general  character.  It  derives  its  name  from 
the  fact  that  these  pavements  were  first  built  in  Brussels,  Bel- 
gium, and  it  is  purely  a  generic  term  designating  any  pavement 
where  blocks  of  a  given  shape  and  size  are  used.  Due  to  the  fact, 
however,  that  most  pavements  of  this  character,  as  laid  in  and 
around  New  York  City  at  least,  were  of  trap  rock,  any  covering 
with  trap  as  the  material  came  to  be  known  by  the  name  of 
Belgian  block. 

The  pavement  possesses  some  advantages  over  cobblestone, 
yet,  on  the  other  hand,  it  lacks  some  of  those  fundamentally 
necessary  characteristics  which  make  an  ideal  covering.  The 


178  HIGHWAY   ENGINEERING 

material  is  so  hard  that  it  is  extremely  durable,  lasting  longer 
than  any  other  stone,  and  because  of  the  shape,  the  blocks  are 
more  stable  when  in  place  than  cobble,  though  not  altogether 
satisfactory  in  this  respect  either;  it  is  cleaner,  and  therefore 
less  unsanitary,  because  of  the  smaller  joints,  but  it  is 
rough  and  noisy,  and,  when  worn  smooth  by  traffic,  lacking 
in  foothold. 

The  blocks  should  be  of  trap  rock  "  of  durable  and  uniform 
quality,  each  measuring  on  the  base  or  upper  surface  not  less 
than  6  nor  more  than  8  ins.  in  length,  and  not  less  than  4  nor 
more  than  6  ins.  in  width,  and  of  a  depth  not  less  than  6  nor 
more  than  8  ins.  Blocks  of  4  ins.  in  width  on  their  face  to  be  not 
less  than  4  ins.  at  the  base.  All  otKer  blocks  of  transverse 
measurement  on  the  base  to  be  not  more  than  1  in.  less  than  on 
the  face,  but  no  block  on  the  face  should  be  of  a  less  width  or 
length  than  4  ins.  Blocks  laid  along  curbs  must  in  all  cases  be 
8  ins.  deep,  and  at  least  one-third  of  the  whole  number  must  be 
of  like  depth.  The  faces  of  the  blocks  must  be  smooth  and  free 
from  all  bunches  or  depressions." 

The  blocks  are  generally  laid  in  parallel  courses  across  the 
street  upon  a  sand  foundation  six  inches  in  depth,  and  covered 
with  a  layer  of  sand  which  is  swept  into  the  joints  until  they  are 
filled,  after  which  the  pavement  is  thoroughly  rammed  until  the 
upper  surface  has  been  brought  to  grade.  A  better  way,  however, 
is  to  lay  them  on  the  diagonal  so  that  the  joints  may  not  then  be 
parallel  to  the  direction  of  traffic.  Though  this  is  expensive,  the 
results  in  wear  seem  to  warrant  the  practice. 

GRANITE    BLOCK 

In  view  of  the  fact  that  both  cobblestone  and  Belgian  block 
have  proven  unsatisfactory  through  their  inherently  weak 
characteristics,  which  more  or  less  unfit  them  for  heavy  grades 
and  traffic,  granite  block  has  replaced  them;  for  it  not  only  com- 


STONE    PAVEMENTS  179 

bines  some  of  the  superior  qualities  of  the  two  former  to  a  degree, 
but  it  possesses  desirable  qualities  of  its  own.  This  result  arises 
chiefly  from  the  judicious  selection  of  a  material  suited  to  the 
needs  of  the  traffic  using  it,  together  with  a  choice  of  shape 
and  size  that  overcome  in  a  measure  the  disadvantages  of 
the  others. 

The  principal  advantages  of  such  a  block  pavement  are  that 
it  is  suitable  to  heavy  grades,  is  durable,  and  furnishes  a  good 
foothold;  but,  on  the  other  hand,  under  certain  atmospheric 
conditions,  i.e.,  when  the  atmosphere  is  saturated  with  moisture, 
or  when  there  is  a  slight  precipitation  of  the  same,  it  becomes 
slippery ;  certain  grades  of  stone  polish  smooth  under  the  action 
of  traffic  with  the  same  result,  it  is  rough  at  best,  noisy,  hard  to 
keep  clean,  and  unsanitary. 

The  very  hardest  rocks,  such  as  basalt  and  the  true  granites, 
are  not  at  all  suited  to  block-stone  pavements;  for  while  it  is  true 
they  are  extremely  durable,  resulting  in  a  minimum  of  wear 
and  consequently  are  long-lived  and  cheap,  they  are  so  hard  as  to 
become  in  time  smooth  and  fail  to  furnish  a  good  foothold. 
Rounded  edges  and  a  slight  amount  of  precipitation  cause  the 
blocks  to  become  as  slippery  as  though  grease  had  been  spread 
over  them. 

A  syenite,  i.e.,  a  granite  in  which  the  hornblende  predomi- 
nates, or  a  hard  sandstone,  such  as  the  Medina  sandstone  found  in 
central  and  western  New  York,  are  very  much  better;  particular- 
ly the  latter,  for  while  it  is  less  durable,  its  physical  constitution  is 
such  that  it  never  polishes,  becomes  slippery,  nor  wears  unevenly. 
In  the  form  of  blocks  this  sandstone  has  been  extensively  used 
both  in  the  western  New  York  and  Lake  cities,  where,  as  in 
Buffalo  and  Rochester,  it  has  given  eminent  satisfaction.  Lime- 
stone has  also  been  employed,  but  it  lacks  durability,  and  wears 
so  unevenly  that  it  is  far  from  being  a  satisfactory  substitute 
for  either  granite  or  certain  grades  of  sandstone. 

SIZE  OF  BLOCK.  Aside  from  other  unfavorable  characteristics, 


180  HIGHWAY   ENGINEERING 

the  size  and  shape  of  both  cobble  and  Belgian  block  are  against 
them.  In  the  former  pavement,  the  stones  are  set  on  end  as  an 
egg  would  be,  receiving  their  support  through  the  lateral  press- 
ure of  the  adjacent  stones,  and  by  the  fact  that  one  end  is  em- 
bedded in  a  layer  of  sand.  This  resulted  in  the  pavement  be- 
coming quickly  rutted,  which  applies,  but  to  a  lesser  degree,  to 
the  Belgian  block.  The  object,  therefore,  in  the  selection  of  a 
paving  stone  was  to  secure  not  only  one  that  was  durable,  but 
one  which,  because  of  its  shape,  should  form  a  stable  pave- 
ment. 

"  For  stability  a  certain  proportion  must  exist  between  the 
depth,  the  length,  and  the  breadth.  The  depth  must  be  such 
that  when  the  wheel  of  a  loaded  vehicle  passes  over  one  edge  of  its 
upper  surface  it  will  not  tend  to  tip  up.  The  resultant  direction 
of  the  pressure  of  the  load  and  the  adjoining  blocks  should  always 
tend  to  depress  the  whole  block  vertically;  where  this  does  not 
happen,  the  maintenance  of  a  uniform  surface  is  impossible.  To 
fulfil  this  requirement,  it  is  not  necessary  to  make  the  blocks 
more  than  7  ins.  deep."  The  width  should  be  such  as  to  give  the 
horses  a  good  foothold,  and  therefore,  in  a  measure,  this  dimen- 
sion depends  upon  the  size  of  a  horse's  hoof.  It  has  been  found, 
and  practice  requires,  that  this  factor  be  from  3  to  4  ins.  The 
length  varies  from  6  to  14  ins.,  but  depends  primarily  upon 

(1)  the  necessity  of  breaking  joints  properly  to  prevent  ruts,  and 

(2)  the  need  of  keeping  blocks  small  to  prevent  splitting  or  becom- 
ing unwieldy. 

Whatever  the  size  of  the  blocks,  however,  all  specifications 
require  that  they  shall  be  square,  i.e.,  parallel  faces  shall  be  of  the 
same  dimensions.  This  precludes  wedge-shaped  stones,  which 
are  to  be  carefully  guarded  against,  as  they  give  but  little  sup- 
port to  adjoining  blocks,  and  are  themselves  unstable  in  the  pave- 
ment. It  is  particularly  essential  also  to  see  that  the  blocks  do 
not  vary  in  depth  by  more  than  one-half  inch,  as  greater  varia- 
tions cause  irregularities  in  the  surface.  All  stones  receive 


STOXE   PAVEMENTS  181 

approximately  the  same  amount  of  ramming  so  that  with  un- 
equal depths  all  blocks  do  not  reach  the  same  firm  and  unyield- 
ing foundation.  When  an  excessive  load  is  applied,  therefore, 
the  shallower  stone  is  forced  down  below  its  neighbors. 

THE  FOUNDATION  for  any  pavement  should  be  properly  pre- 
pared, and  cobble  or  block  stone  is  no  exception  to  this  rule. 
To  accomplish  this,  the  subgrade  of  natural  earth  should  be  care- 
fully examined,  unsatisfactory  material  having  its  place  filled 
with  fresh  earth  or  sand,  and  the  resulting  foundation  brought  to 
grade,  by  rolling  so  as  to  form  an  evenly  compacted  surface. 
Upon  this  surface  is  usually  placed  what  is  termed  the  cushion 
coat, which  is  nothing  more  nor  less  than  a  layer  of  sand,  and  which 
acts,  as  the  name  indicates,  as  a  cushion  for  the  blocks  of  stone  to 
be  placed  upon.  These  blocks,  no  matter  how  carefully  dressed 
to  dimensions,  have  irregular  surfaces  with  projections  or  de- 
pressions on  the. several  faces.  If  in  this  condition  they  were 
placed  upon  an  unyielding  foundation,  or  even  upon  a  semirigid 
one,  it  would  happen  that  most  of  them  would  fail  to  receive 
uniform  support  over  the  under  face,  with  the  result  that  the 
pavement  would  be  speedily  rutted  and  broken  up  by  hollow 
spots.  The  sand  or  cushion  coat  prevents  this,  for  it  quickly 
adjusts  itself  to  the  irregularities  of  the  surface  with  which  it  is  in 
contact,  so  that  any  load  applied  to  the  upper  surface  of  the 
block  is  transmitted  uniformly  through  the  sand  to  the  founda- 
tion below.  This  is  as  it  should  be,  for  if  the  total  load  on  any 
one  block,  when  a  wheel  is  passing  over  it,  were  carried  to  the 
subgrade  by  only  a  small  portion  of  the  block — as,  for  example, 
by  means  of  a  downward  projecting  point — the  intensity  of 
pressure  would  be  so  great  as  to  cause  the  block  to  break  through 
the  surface  of  the  subgrade,  and  depress  the  surface  beneath  that 
of  the  neighboring  stones.  The  cushion  coat  should  never  be 
less  than  one  inch  in  depth,  and  should  be  of  clean,  dry  sand. 
If  it  is  dirty,  that  is,  if  it  contains  loam  or  vegetable  matter,  it 
will  not  be  so  mobile  in  the  former  case,  and  in  the  latter  the 


182  HIGHWAY    ENGINEERING 

process  of  decomposition  will  leave  voids.  If  damp  -or  wet,  it 
should  be  heated  to  drive  off  the  moisture,  since  the  presence  of 
the  same  causes  heaving  under  the  action  of  frost. 

LAYING  THE  STONE.  Upon  this  cushion  coat  of  sand,  the 
blocks  should  be  laid  in  parallel  courses  across  the  street,  from 
the  sides  to  the  centre,  with  the  long  edge  perpendicular  to  the 
axis  of  the  street.  The  blocks  should  break  joints  with  those 
in  the  rows  adjoining  by  not  less  than  two  inches,  and  these 
joints  should  be  as  small  as  possible.  Wide  joints  increase  the 
wear  and  do  not  improve  the  foothold.  The  blocks  are  then 
brought  to  the  required  grade  and  profile  by  ramming,  for  which 
purpose  a  rammer  of  about  fifty  pounds  in  weight,  with  a  butt 
not  less  than  three  inches,  is  used.  This  ramming  should  be 
continued  until  the  blocks  sink  no  further  under  the  application 
of  the  blows,  and  if  they  do,  then  they  should  be  removed  and 
more  sand  placed  beneath  them.  If  any  of  the  blocks,  on  the 
other  hand,  rise  above  the  general  elevation,  they  must  be  re- 
moved, and  reset  till  the  desired  condition  is  obtained. 

THE  JOINTS  are  filled  with  a  variety  of  materials, such  as  sand, 
a  grout  of  cement  mortar,  bituminous  cement,  etc.  The  pur- 
pose of  the  joint  filling  is,  of  course,  to  prevent  any  moisture  from 
reaching  the  foundation,  so  that,  all  other  things  being  equal, 
that  which  best  satisfies  this  requirement  is  the  most  satisfactory. 
For  this  reason  sand  is  not  so  good  as  either  the  cement  mortar  or 
the  bituminous  cement.  But  the  mortar  used  as  a  joint  filling 
is  so  easily  chipped  under  the  action  of  traffic  that  the  better 
specifications  call  for  the  bituminous  cement.  This  latter  may 
be  tar  distillate,  a  mixture  of  tar  distillate  and  refined  asphaltum, 
or  various  mixtures  of  asphaltum,  creosote,  and  coal  tar. 

The  specifications  for  New  York  City  prescribe: 

Refined  Trinidad  asphaltum 20  parts. 

No.  4  coal-tar  distillate 100  parts. 

Residuum  of  petroleum 3  parts. 

Such  a  joint  filling  should  be  brought  hot  to  the  place  where 


STONE   PAVEMENTS  183 

the  stone  is  being  laid,  and  should  be  kept  so  until  used.  When 
the  pavement  is  ready  for  the  joint  filling,  the  joints  are  first  filled 
with  small  clean  pebbles  or  gravel  to  within  two  inches  of  the 
surface,  and  the  bituminous  cement  or  other  mixture  is  then 
poured  into  the  joints.  More  gravel  is  then  swept  into  the  joints, 
followed  by  more  cement,  and  this  procedure  is  continued  until 
the  cement  flushes  to  the  top.  On  top  of  this  finally  is  then 
placed  fine  gravel  or  sand.  The  amount  of  cement  to  be  used: 
will  vary  with  the  size  of  the  joints,  but  will  average  between 
three  and  twelve  gallons  per  square  yard  of  pavement. 

The  method  of  laying  the  blocks  at  intersections  will  be  the 
same  as  for  brick  pavements  while  on  steep  grade,  to  afford  bet- 
ter foothold,  they  may  be  placed  on  edge. 

The  complete  specifications  governing  the  laying  of  granite- 
block  pavements  in  New  York  City  are  appended  below. 

SPECIFICATIONS 

FOR  REGULATING,  GRADING,  AND  PAVING  OR  REPAVING  WITH 
A  GRANITE-BLOCK  PAVEMENT  ON  A  CONCRETE  FOUNDATION 
THE  ROADWAY  OF 

FROM    

To '.;... 

TOGETHER  WITH  ALL  WORK  INCIDENTAL  THERETO. 

1.  EXTENT  OF  WORK.     The  work  shall  consist  of  regulating 
and  grading  the  entire  roadway  (or  if  the  street  is  already  paved, 
of  removing  the  old  pavement),  setting  and  resetting  curb,  laying 
sidewalks  where  required,  and  laying  a  granite-block  pavement 
and  all  work  incidental  thereto,  all  in  accordance  with  the  plans 
and  specifications  on  file  in  the  office  of  the  Bureau  of  Highways. 

2.  OBSTRUCTIONS.     The  contractor  shall  remove  at  his  own 
expense,  when  directed  by  the  engineer,  any  encumbrances  or 
obstructions  on  the  line  of  work,  located  or  placed  there  prior  to 
or  after  its  commencement. 


184  HIGHWAY   ENGINEERING 

CATCH-BASINS,  MANHOLE  HEADS,  ETC.  Such  catch-basins, 
manhole  frames  and  heads  for  sewers,  water  pipes  or  other  con- 
duits belonging  to  the  City  on  the  line  of  the  work,  as  may  be 
designated,  shall  be  reset  to  the  new  grades  and  lines  by  the 
contractor  without  extra  charge  therefor,  and  they  shall  be 
brought  to  such  grades  with  brick  masonry  of  the  same  thickness 
as  that  originally  used,  laid  in  hydraulic  cement  mortar. 

4.  NOISELESS    MANHOLE   COVERS. — Asphalt-filled    noiseless 
covers,  complete,  for  water  and  sewer  manholes  of  the  design 
approved  by  the  engineer,  shall  be  furnished  and  set  wherever 
directed  by  the  engineer.     They  shall  be  made  according  to 
general  details  to  be  furnished  to  the  contractor  and  of  such  size 
as  will  fit  the  present  manhole  heads.    The  old  covers  to  remain 
the  property  of  the  City. 

5.  REMOVAL  AND  OWNERSHIP  OF  OLD  MATERIALS.    All  old 
material  which  will  not  be  used  in  the  work,  excepting  bridge 
stone  and  specification  paving  stone,  shall  become  the  property  of 
the  contractor  and  be  removed  by  him;  the  remainder,  as  specified 
above,  shall  be  delivered  when  required,  and  piled  in  such  cor- 
poration yard  or  elsewhere  as  the  engineer  may  determine,  and 
all  at  the  expense  of  the  contractor. 

6.  PREPARATION  OF  FOUNDATION.     When  the  old  material 
has  been  removed,  that  to  be  used  again  shall  be  compactly  piled 
on  the  side  and  the  roadway  graded  to  the  required  shape  and 
depth  below  the  proposed  finished  pavement.     All  unsuitable 
material  shall  be  removed  and  replaced  with    that   which  is 
satisfactory. 

7.  On  the  roadbed  graded  and  prepared  as  hereinafter  set 
forth,  the  stones  shall  be  relaid  at  right  angles  to  the  line  of  the 
street.     They  shall  be  well  bedded  on  two  inches  of  sand,  with 
surface  joints  not  exceeding  three-quarter  (f )  inch,  the  joints  to 
be  brushed  full  of  the  same  material  and  the  stones  rammed  to  a 
solid,  unyielding  foundation,  with  their  top  surface  conforming 
to  the  lines  and  grades  shown  by  the  plan  of  the  work. 


STONE    PAVEMENTS  185 

8.  INSPECTION  AND  PILING  OF  MATERIAL.    The  material  for 
construction  when  brought  upon  the  street  shall  be  neatly  piled 
so  as  to  present  as  little  obstruction  to  travel  as  possible.     No 
material  shall  be  used  without  having  been  first  inspected  and  ac- 
cepted by  the  engineer,  the  contractor  furnishing  all  labor  neces- 
sary for  inspection  without  any  charge.     Should  the  work  be 
suspended  for  any  cause,  the  materials  shall  be  removed  from 
the  line  of  the  work  at  the  direction  of  the  engineer,  and  unless  so 
removed  by  the  contractor  upon  notice  from  the  said  engineer, 
they  will  be  removed  by  the  president,  and  the  expense  thereof 
charged  to  the  contractor. 

9.  CITY  MONUMENTS.    The  contractor  shall  not  excavate 
around  such  city  monuments  and  bench-marks  as  may  come 
within  the  limits  of,  or  be  disturbed  by  the  work  herein  contem- 
plated nearer  than  five  (5)  feet,  or  in  any  manner  disturb  the 
same,  but  shall  cease  work  at  such  locations  until  the  said  monu- 
ments or  marks  have  been  referenced  and  reset  or  otherwise  dis- 
posed of  by  the  chief  engineer  of  the  Bureau  of  Highways.      The 
necessary  labor  to  remove,  care  for,  and  reset  all  such  monuments 
and  bench-marks  shall  be  furnished  without  charge  therefor  by 
the  contractor. 

10.  CURBSTONE.     Old  curbstone  which  can  be  redressed  to  a 
top  width  of  not  less  than  four  and  one-half  (4J)  inches  and  not 
less  than  sixteen  (16)  inches  deep  and  are  of  the  quality  hereafter 
specified,  shall  be  redressed,  rejointed,  and  reset  as  directed 
below. 

11.  QUALITY  OF.     New  curbstones  shall  be  free  from  seams 
and  other  imperfections  and  equal  in  quality  to  the  best  North- 
River  bluestone.     They  shall  be  (     )  inches  in  depth, 
and  from  three  and  one-half  (3J)  to  eight  (8)  feet  in  length,  and 
not  less  than  five  inches  in  thickness,  except  as  noted  for  bottom 
of  curb. 

12.  How  DRESSED.     The  face  for  a  depth  of  nine  (9)  inches 
and  the  top  on  a  bevel  of  one-half  (J)  an  inch  in  its  width  of  five 


186  HIGHWAY  ENGINEERING 

(5)  inches  shall  be  dressed  to  a  surface  which  shall  be  out  of  wind 
and  shall  have  no  depressions  measuring  more  than  one-quarter 
of  an  inch  from  a  line  or  straight  edge  of  the  same  length  as  the 
curbstone.  The  remainder  of  the  face  shall  be  free  from  projec- 
tions of  more  than  one-half  (J)  an  inch  and  the  back  for  three 
(3)  inches  down  from  the  top  shall  have  no  projections  greater 
than  one-quarter  (})  of  an  inch  measured  from  a  plane  at  right 
angles  to  the  top.  The  bottom  of  the  curb  shall  be  rough- 
squared  with  a  width  of  not  less  than  three  (3)  inches. 

13.  JOINTS  OF.    CURVED  CURB.     For  the  full  width  of  the 
stone  for  a  distance  down  of  four  (4)  inches  from  the  top,  and 
therebelow  for  a  width  of  one  and  one-half  inches  back  from  the 
face  to  a  point  twelve  (12)  inches  below  the  top  of  the  curb,  the 
ends  shall  be  squarely  jointed  with  no  depression  greater  than 
three-eighths  of  an  inch,  measured  from  a  straight  edge.     Curved 
curb  corners  shall  be  cut  with  true  radial  joints  and  be  set  ac- 
curately to  such  a  radius  as  may  be  required  in  three  (3)  foot 
lengths.     It  shall  be  paid  for  as  straight  curb,  and  must  comply 
in  all  respects  with  the  above  requirements  therefor.     The  cost 
of  excavation  necessary  for  curb-setting  shall  be  included  in  the 
price  paid  per  linear  foot  of  curb.     The  sample  of  the  curbstone 
showing  the  dressing  and  the  jointing  required  can  be  seen  at  the 
office  of  the  chief  engineer  of  the  Bureau  of  Highways. 

WHEN  SET  IN  CONCRETE.  The  curb  shall  be  set  on  concrete 
as  shown  by  detail  on  plan,  and  shall  be  set  truly  to  line  and  grade 
on  a  face  batter  of  one  and  a  half  inches  in  its  depth. 

14.  CHARACTER  OF  CONCRETE.     The  concrete  foundation  for 
curbstone  shall  be  not  less  than  six  (6)  inches  thick  and  seventeen 
(17)  inches  in  width  and  be  of  the  materials  and  proportions  here- 
inafter described,  except  that  the  broken  stone  shall  be  not  less 
than  one-quarter  (J)  nor  more  than  one  and  a  quarter  (1J) 
inches  maximum  dimensions;    the  curb  shall  be  immediately 
bedded  on  the  centre  thereof,  with  a  bearing  for  its  full  length  as 
soon  as  the  concretejs  laid,  and  it  shall  be  at  once  backed  up  with 


STONE    PAVEMENTS  187 

concrete  for  a  width  of  six  (6)  inches,  extending  from  the  bottom 
bed  to  within  four  (4)  inches  of  the  top  of  the  stone.  The  con- 
crete so  used  will  be  paid  for  at  the  general  price  per  cubic  yard 
for  concrete. 

15.  IN  FRONT  OF  CEMENT  WALK.    When  curb  is  set  in  front 
of  a  monolithic  walk,  the  space  between  the  curb  and  sidewalk 
foundation  shall  be  completely  filled  with  concrete  similar  to 
that  described  above,  to  within  two  (2)  inches  of  the  top;  the 
remaining  space  to  be  filled  with  Portland  cement  of  the  quality 
hereinafter  specified,  mixed  with  an  equal  part  of  crushed  stone 
used  for  wearing  surface  of  such  walks.     Wherever  curbstones, 
however  set,  shall  have  become  displaced  or  damaged  from  any 
cause,  such  curbstone  shall  be  reset  or  new  ones  shall  be  fur- 
nished in  their  place  and  no  compensation  therefor  shall  be 
allowed. 

16.  SIDEWALKS.     On  repaving  work  the  first  course  of  flag- 
stones interfering  with  the  work  of  curb-setting  shall  be  taken  up 
and  relaid  to  the  new  curb  grade,  at  the  expense  of  the  contractor. 
Any  damage  done  by  the  contractor  to  sidewalks  in  curb-setting, 
handling,  or  in  the  storage  of  materials  shall  be  made  good  by 
him,  at  his  own  expense,  as  shall  be  directed  by  the  engineer. 

17.  How  LAID.     All  flagging  to  be  relaid  shall  be  firmly  and 
evenly  bedded  to  the  grade  and  pitch  required,  on  three  (3)  inches 
of  steam  ashes  or  sand  free  from  loam  or  clay  and  the  work 
brought  to  an  even  surface,  with  all  joints  close  and  thoroughly 
filled  for  the  full  depth  with  cement  mortar  composed  of  equal 
parts  of  the  best  Portland  cement  and  clean,  sharp  sand,  and  left 
clean  on  the  surface;  and  all  earth,  debris,  and  surplus  material 
shall  be  removed  from  each  block  and  the  sidewalks  swept  clean 
as  soon  as  the  work  thereon  has  been  completed. 

18.  CONCRETE. — CEMENT. — PROPORTION.   The  concrete  shall 
be  made  of  the  best  quality  of  Portland  cement,  samples  of  which 
must  be  submitted  at  least  ten  (10)  days  (Sundays  and  holidays 
excluded)  before  using,  for  the  inspection  and  approval  of  the 


188  HIGHWAY   ENGINEERING 

chief  engineer.     All  cement  shall  be  of  a  uniform  quality,  color, 
and  weight,  and  briquettes  of  one  (1)  square  inch  section  shall 
develop  or  exceed  the  following  tensile  strength  : 
Neat — four  (4)  hours  in  moist  air,  twenty  (20)  hours 

in  water 200  pounds 

Neat — one  (1)  day  in  air,  six  (6)  days  in  water 400  pounds 

One  (1)  of  cement,  three  (3)  of  sand,  one  (1)  day  in 

air,  six  (6)  days  in  water. 150  pounds 

The  concrete  shall  be  composed  of  one  (1)  part  of  cement,  three 
(3)  parts  of  sand,  and  six  (6)  parts  of  broken  stone.  The  unit  of 
measure  shall  be  the  barrel  of  cement  as  packed  by  and  received 
from  the  manufacturer. 

19.  SAND  AND  STONE.    The  sand  shall  be  clean,  coarse,  and 
sharp,  and  be  free  from  loam  or  dirt.     The  broken  stone  shall  be 
of  trap,  granite,  or  limestone  or  such  other  stone  taken  from  the 
line  of  work  as  shall  be  satisfactory  in  the  judgment  of  the 
engineer.     It  shall  be  entirely  free  from  dust  and  dirt,  and  be  of 
graded  sizes  such  that  all  will  pass  through  a  revolving  circular 
screen  having  holes  two  and  one-half  (2  J)  inches  in  diameter  and 
be  retained  by  a  screen  having  holes  one-half  (J)  inch  in  diameter. 
The  sand  and  stone  shall  be  placed  upon  board  platforms  and  be 
kept  free  from  dirt,  and  the  cement  shall  be  properly  blocked  up 
and  protected  from  dampness. 

20.  MIXING.    The  sand  and  cement  shall  be  mixed  dry,  then 
made  into  mortar  by  the  addition  of  water,  when  the  broken 
stone  shall  be  added  and  the  whole  mass  thoroughly  mixed. 
The  concrete  shall  then  be  spread  upon  the  subgrade  and  rammed 
so  as  to  fill  all  the  voids  of  the  stone  with  mortar  and  bring  the 
surface  exactly  ten  (10)  inches  below  the  finished  pavement. 
If  a  machine  be  used  for  mixing,  the  above  operation  may  be 
varied  as  may  be  required.     No  concrete  shall  be  used  that  has 
been  mixed  more  than  one-half  hour.    The  concrete  shall  be  pro- 
tected from  the  weather  when  deemed  necessary  by  the  engineer. 
Before  laying  concrete  to  connect  with,  rest  upon,  or  overlap 


STONE   PAVEMENTS  189 

concrete  previously  laid,  the  entire  surface  of  contact  of  the 
latter  shall  be  swept  and  washed  clean  of  all  dirt  and  mortar 
particles. 

21.  No  CARTING.    No  horses,  carting,  or  wheeling  shall  be 
allowed  on  the  concrete  before  the  same  has  set,  except  on  planks 
furnished  and  laid  by  the  contractor. 

22.  THICKNESS.     The  concrete  foundations  shall  be  six  (6) 
inches  thick,  except  where  otherwise  specially  ordered. 

23.  BRIDGESTONES. — QUALITY.     When  required,  old  bridge- 
stones  shall  be  redressed,  rejointed,  and  relaid  as  hereafter  direct- 
ed for  new  bridgestones,  and  for  such  purpose  shall  be  hauled  to 
the  necessary  point  or  points  by  the  contractor.     Bridgestone 
broken  by  being  so  hauled,  redressed,  or  relaid  shall  be  replaced 
by  the  contractor  at  his  own  expense.     New  bridgestones  shall  be 
of  the  same  quality  of  granite  as  the  blocks,  free  from  all  imper- 
fections. 

24.  DIMENSIONS.    They  shall  be  eighteen  (18)  inches  wide, 
of  a  uniform  thickness,  not  less  than  six  or  more  than  eight  (8) 
inches  hi  depth,  and  from  three  and  one-half  (3J)  to  eight  (8) 
feet  in  length,  except  that  in  special  cases,  between  railroad 
tracks,  they  may  be  of  such  dimensions  as  may  be  approved 
by  the  chief  engineer  of  the  Bureau  of  Highways. 

25.  DRESSING.    The  top  shall  be  dressed  to  a  surface  not 
varying  in  evenness  more  than  one-quarter  (J)  of  an  inch.     The 
sides  and  ends  shall  be  dressed  square  down  and  the  latter  cut  to 
a  transverse  bevel  of  six  (6)  inches  in  the  width  or  to  such  other 
bevel  as  may  be  directed,  and  the  jointing  from  top  to  bottom 
shall  give  joints  not  greater  than  one-quarter  ( J)  of  an  inch. 

26.  LAYING.  The  bridgestones  shall  be  laid  in  parallel  courses 
separated  by  a  corner  of  granite  blocks,  and  shall  be  well  and 
firmly  bedded  on  a  layer  of  sand  spread  on  the  foundation  as  pre- 
pared for  the  pavement.     The  transverse  joints  shall  be  broken 
by  a  lap  of  at  least  one  (1)  foot,  and  be  so  laid  as  not  to  be  parallel 
to  vehicular  traffic. 


190  HIGHWAY   ENGINEERING 

27.  BLOCKS.     The  blocks  to  be  used  shall  be  of  a  durable, 
sound,  and  uniform  quality  of  granite,  each  stone  measuring  not 
less  than  eight  (8)  inches,  nor  more  than  twelve  (12)  inches  in 
length;  not  less  than  three  and  one-half  (3J)  nor  more  than  four 
and  one-half  (4J)  inches  in  width,  and  not  less  than  seven  (7) 
nor  more  than  eight -(8)  inches  in  depth,  and  the  stones  shall  be  of 
the  same  quality  as  to  hardness,  color,  and  grain.     No  outcrop, 
soft,  brittle,  or  laminated  stone  will  be  accepted.     The  blocks  are 
to  be  rectangular  on  top  and  sides,  uniform  in  thickness,  to  lay 
closely,  and  with  fair  and  true  surfaces,  free  from  bunches. 
Over  special  constructions,  the  blocks  may  be  of  dimensions  other 
than  above  specified,  when  approved  by  the  engineer.     The  stone 
from  each  quarry  shall  be  piled  and  laid  separately  in  different 
sections  of  the  work,  and  in  no  case  shall  the  stones  from  different 
quarries  be  mixed. 

28.  PAVING  CEMENT.    The  paving  cement  to  be  used  in  filling 
the  joints  between  and  around  the  paving  blocks  and  bridge- 
stones  when  laid  on  concrete,  as  hereafter  provided,  shall  be  com- 
posed of  twenty  (20)  parts  of  refined  asphalt  and  three  (3)  parts 
of  residuum  oil,  mixed  with  one  hundred  (100)  parts  of  coal-tar 
pitch  such  as  is  ordinarily  numbered  four  (4)  at  the  manufactory, 
the  proportions  to  be  determined  by  weight.     The  paving  cement 
must  be  heated  as  needed  for  immediate  use. 

29.  SAND. — On  the  concrete  foundation,  as  designated,  shall 
be  laid  a  bed  of  clean,  coarse  dry  sand  to  such  depth  (in  no  case 
less  than  one  and  a  half  [1J]  inches),  as  may  be  necessary  to 
bring  the  surface  of  the  pavement,  when  thoroughly  rammed,  to 
the  proper  grade. 

30.  LAYING.     On  this  sand  bed,  and  to  the  grade  and  crown 
specified,  shall  be  laid  the  stone  blocks  at  right  angles  to  the  line 
of  the  street  or  at  such  angle  as  may  be  directed.     Each  course  of 
blocks  shall  be  laid  straight  and  regularly,  with  the  end  joints  by 
a  lap  of  at  least  three  (3)  inches,  and  in  no  case  shall  stone  of 
different  width  be  laid  in  the  same  course  except  on  curbs.     All 


STONE   PAVEMENTS  191 

joints  shall  be  close  joints  except  that  when  gravel  filling  is  used, 
the  joints  between  courses  shall  be  not  more  than  three-quarters 
( J)  of  an  inch  in  width. 

31.  ON  SAND  FOUNDATION.    As  the  blocks  are  laid  they  shall 
be  covered  with  sharp,  coarse  sand,  free  from  gravel,  which  shall 
be  raked  or  brushed  until  all  the  joints  become  filled  therewith; 
the  blocks  shall  then  be  thoroughly  rammed  to  a  firm,  unyielding 
bed,  with  a  uniform  surface  to  conform  to  the  grade  and  crown  of 
the  street.    It  shall  be  covered  with  a  good  and  sufficient 
second  coat  of  clean,  sharp  sand,  and  shall  immediately  thereafter 
be  thoroughly  rammed  until  the  work  is  made  solid  and  secure; 
and  so  on  until  the  whole  of  the  work  shall  have  been  well  and 
faithfully  completed.    No  truck  or  vehicle  shall  be  allowed  to 
pass  over  it  until  the  final  ramming  has  been  completed  as  above, 
but  no  ramming  shall  be  done  within  twenty  feet  of  the  face  of  the 
work  that  is  being  laid. 

32.  ON  CONCRETE  FOUNDATION.    After  the  blocks  are  laid  on 
a  concrete  foundation,  they  shall  be  covered  with  a  clean,  hard, 
and  dry  gravel,  which  shall  have  been  artificially  heated  and  dried 
in  proper  appliances,  placed  in  close  proximity  to  the  work,  the 
gravel  to  be  brushed  in  until  all  the  joints  are  filled  therewith  to 
within  three  (3)  inches  of  the  top.     The  gravel  must  be  washed 
white  quartz  and  be  entirely  free  from  sand  or  dirt  and  must 
have  passed  through  a  sieve  of  five-eighth  (f )  inch  mesh  and  been 
retained  by  a  three-eighth  (f )  inch  mesh. 

33.  RAMMING.    The  blocks  must  then  be  thoroughly  rammed 
and  the  ramming  repeated  until  they  are  brought  to  an  unyield- 
ing bearing  with  a  uniform  surface,  true  to  the  given  grade  and 
crown.     No  ramming  shall  be  done  within  twenty  (20)  feet  of  the 
face  of  the  work  that  is  being  laid. 

34.  TEMPERATURE  OF  PAVING  CEMENT.    The  boiling  paving 
cement,  heated  to  a  temperature  of  300  °  Fahrenheit,  and  of  the 
composition  hereinbefore  described,  shall  then  be  poured  into 
the  joints  until  the  same  are  full,  and  remain  full  to  the  top  of  the 


192  HIGHWAY   ENGINEERING 

gravel.  Hot  gravel  shall  then  be  poured  along  the  joints  until 
they  are  full  flush  with  the  top  of  the  blocks,  when  they  shall 
again  be  poured  with  the  paving  cement  till  all  voids  are  com- 
pletely filled. 

35.  The  appliances  for  heating  paving  cement  shall  be  suf- 
ficient in  number  and  of  such  efficiency  as  will  permit  the  pourers 
to  closely  follow  the  back  rammers,  and  all  joints  of  the  finally 
rammed  pavement  shall  have  been  filled  with  paving  cement  as 
above  noted,  before  the  cessation  of  the  work  for  the  day  or  any 
other  cause. 

36.  MORTAR  BED  BY  CAR  TRACKS.  On  either  or  both  sides 
of  the  rails  of  car  tracks,  as  may  be  designated,  the  contractor 
shall  lay  on  the  concrete  foundation  adjacent  thereto  a  bed  of 
Portland-cement  mortar,  of  the  quality  hereinbefore  set  forth, 
one  of  cement  to  three  of  sand,  in  which  long  and  short  blocks, 
alternating  and  toothing  into  the  pavement  as  headers,  shall  be 
bedded. 

37.  This  mortar  bed  shall  extend  outward  from  the  rail  to  a 
width  of  four  (4)  inches  beyond  the  outer  edge  of  the  long  blocks, 
and  it  shall  not  be  prepared  for  or  laid  to  an  extent  greater  than 
fifteen  (15)  feet  in  advance  of  the  pavers,  and  before  laying,  the 
concrete  shall  have  been  first  thoroughly  swept  and  wetted. 

38.  THICKNESS  OF  MORTAR  BED.    The  top  of  concrete  shall 
be  at  such  elevation  and  the  mortar  bed  shall  be  of  such  thickness 
(in  no  case  less  than  1J  inches)  that  when  the  paving  blocks 
are  therein  embedded,  there  shall  remain  1  inch  of  mortar  under 
the  stones,  their  top  surface  shall  be  J  of  an  inch  above  the 
tread  of  the  adjacent  rail  (except  at  guards  or  other  projections 
when  they  will  be  flush  with  the  latter)  and  the  bottom  of  the 
stones  shall  be  locked  in  position  by  the  displaced  mortar  rising 
in  the  joints. 

39.  No  ramming  of  toothing  stones  shall  be  allowed  and  they 
shall  be  set  carefully  to  grade,  with  joints  filled  and  poured  as 
above,  and  be  properly  protected  until  the  mortar  is  set. 


STONE    PAVEMENTS  193 

40.  No  CARTING  ON  PAVEMENT.    No  horse,  cart%  truck,  or 
vehicle  of  any  description  shall  be  permitted  to  stand  on,  or 
pass  over,  the  pavement  until  the  joints  have  been  finally  poured 
with  cement  as  above  and  the  same  has  had  time  to  harden,  and, 
by  car  tracks,  the  contractor  shall  furnish  men  to  pass  cars  there- 
over. 

41.  When  each  section  of  the  street  has  been  completed, 
travel  is  to  be  allowed  thereon,  if  required  by  the  engineer,  and 
at  the  time  of  completion  of  the  entire  work  and  before  the  final 
payment,  the  contractor  will  be  required  to  make  good  at  every 
point  any  defect  which  is  the  result  of  non-compliance  with  any 
of  the  provisions  of  this  contract. 

In  case  of  repairs  it  shall  be  required  that  such  repairs  be  made 
with  a  pavement  equal  to  the  above  described. 

42.  APPROACHES.    The  curbstones,  crosswalks,  and  gutters 
of  the  adjoining  pavements  and  all  pavements  abutting  the  new 
work  shall  be  readjusted  and  brought  to  the  new  grades  and  lines 
to  the  extent  deemed  necessary  by  the  engineer,  and  such  read- 
justment of  curb  and  pavement  shall  include  rejointing,  resetting, 
and  relaying  as  hereinbefore  provided,  at  the  prices  stipulated. 

43.  CLEARING  UP.    All  surplus  materials,  earth,  sand,  rub- 
bish, and  stones,  except  such  stones  as  are  retained  by  order  of 
the  engineer,  are  to  be  removed  from  the  line  of  the  work,  block 
by  block,  as  rapidly  as  the  work  progresses.     All  material  cover- 
ing the  pavement  and  sidewalks  shall  be  swept  into  heaps  and 
immediately  removed  from  the  line  of  the  work. 

44.  During  the  prosecution  of  the  work  the  contractor  shall 
keep  the  footway  clean  by  sweeping.     When  material  is  removed, 
the  sidewalk  must  be  immediately  swept  clean  by  the  contractor, 
and  when  public  or  local  inconvenience  is  caused  by  dust  the 
contractor  shall  water  any  piles  or  surface  of  earth  or  the  side- 
walks, or  pavement  foundation  during  sweeping  when  and  where 
necessary  or  whenever  required  by  the  engineer  to  do  so. 


CHAPTER  VIII 

BRICK  PAVEMENTS 

RECORDS  seem  to  indicate  that  the  first  pavements  of  brick  to 
be  used  in  the  United  States  were  laid  about  1870  in  Charlestown, 
W.  Va.,  and  in  several  of  the  smaller  towns  of  the  Middle  West 
where  clay  is  plentiful.  In  Holland,  however,  brick  had  been 
employed  for  such  purposes  as  early  as  the  thirteenth  century, 
and  is  still  extensively  so  used.  Recently  its  use  in  the  smaller 
towns  and  in  localities  where  clay  is  abundant  has  been  quite 
extensive,  and  the  many  superior  characteristics  which  a  brick 
pavement  possesses,  particularly  for  light  traffic,  warrants  its 
choice.  The  popularity  of  this  form  is  indicated  by  the  United 
States  Report  for  the  decade  ending  with  1900.  During  that 
period,  of  the  hard  pavements  laid  33  per  cent  were  of  brick; 
this  being  exceeded  only  by  asphalt  with  43  per  cent,  and  followed 
by  granite  block  with  10  per  cent,  wooden  block  9  per  cent,  and 
miscellaneous  5  per  cent.  The  latest  report  of  the  United  States 
Census  Bureau,  that  for  1903,  regarding  pavements  shows  that  in 
cities  of  over  25,000  inhabitants,  of  the  hard  pavements  in  place 
31  per  cent  was  of  asphalt,  25  per  cent  of  granite  block,  19  per 
cent  of  brick,  14  per  cent  of  wooden  block,  and  11  per  cent  of 
cobble,  but  this  is  hardly  indicative  since  in  towns  of  less  than 
25,000  brick  is  much  more  generally  used  than  in  towns  exceeding 
this  population. 

The  advantages  of  brick  as  a  paving  material  may  be  enumer- 
ated as  follows : 

(1)  It  affords  a  good  foothold. 

(2)  It  materially  reduces  the  tractive  force. 

(3)  The  pavement  is  fairly  durable  under  moderate  traffic. 

194 


BRICK    PAVEMENTS  195 

(4)  It  is  not  noisy. 

(5)  It  is  easily  cleaned,  and  therefore  sanitary. 

(6)  It  is  easily  repaired. 

(7)  It  requires  no  expensive  plant,  and  hence  good  for  small 
towns. 

Generally  speaking,  "  it  seems  to  be  able  to  withstand  misuse 
in  construction,  especially  in  the  less  heavily  travelled  streets  of 
the  smaller  communities,  better  than  any  other  paving  material, 
and  as  a  consequence  is  one  of  the  most  popular  materials  for  this 
class  of  towns.  In  the  larger  cities,  where  pavements  are  more 
scientifically  constructed,  brick  is  also  popular,  not  only  because 
in  them  it  is  better  laid,  but  it  has  a  smoother  surface  and  is  less 
slippery  than  most  other  hard  pavements." 

The  figures  which  follow,  taken  from  a  report  on  street  paving 
by  J.  W.  Alvord,  1903,  show  graphically  two  reasons  for  the 
preference  for  brick  pavements. 

One  demonstrates  the  relative  loads  that  may  be  hauled  (on 
the  various  pavements)  with  the  same  expenditure  of  energy,  and 
in  this  respect  brick  is  placed  first.  The  other  shows  the  rela- 
tive amount  of  labor  required  to  clean  the  various  pavements,  and 
here  again  brick  takes  lowest  place,  being  equalled,  but  not  ex- 
ceeded, in  economy  of  cleaning  by  asphalt  and  rectangular  wood- 
en block.  On  the  other  hand,  brick  is  extremely  likely  to  be 
lacking  in  uniformity,  both  as  to  shape  and  quality,  unless  great 
care  is  exercised  in  the  manufacture,  and  in  consequence  wears 
unevenly. 

The  Brick.  A  paving  brick  differs  from  an  ordinary  building 
brick  both  in  shape  and  physical  characteristics.  It  is  larger, 
harder,  tougher,  less  porous,  and  stronger  in  every  way  than 
the  latter.  Generally  speaking,  the  same  conditions  that  govern 
the  selection  of  size  in  granite  block  for  paving  should  determine 
that  of  a  brick,  but  there  are  certain  factors  in  the  manufacture 
that  preclude  these  dimensions  being  used.  "  If  the  brick  is 
made  too  long,  it  is  liable  to  warp  either  in  the  preliminary  drying 


196 


HIGHWAY   ENGINEERING 


or  while  being  burned  in  the  kiln.  If  it  is  too  thick,  so  that  the 
clay  in  the  interior  is  vitrified  with  difficulty,  it  is  probable  that 
when  sufficient  heat  has  been  applied  to  insure  the  proper  vitri- 
fication to  the  central  part  of  the  brick,  the  outside  will  have  been 
damaged  and  the  brick  not  of  uniform  texture  throughout,  so 


FIG.  57. 

that  in  determining  the  thickness  the  same  rule  will  not 
apply  to  all  clays,  as  some  clays  will  vitrify  more  readily  than 
others."* 

The  above,  a  few  minor  reasons  and  experience,  have  led 
manufacturers  and  engineers  to  select  bricks  for  paving  of  the 
two  following  sizes:  2J  ins.  X  4  ins.  X  8J  ins.  and  3  ins.  X  4  ins. 
X  9  ins.,  the  latter  being  termed  blocks.  Formerly  this  uniforrn- 


*  Tillson. 


BRICK   PAVEMENTS 


197 


ity  in  size  did  not  exist,  and  it  has  been  only  after  years  of  ex- 
perience and  experimenting  with  various  shapes  and  sizes  that 
the  above  dimensions  have  resulted. 

The  form  of  the  brick  is,  without  exception,  rectangular.  In 
cases  the  edges  are  rounded  off;  in  others,  square.  Some  bricks 
will  have  a  groove  in  them  to  hold  the  joint  filler,  while  others 
will  have  a  small  button  on  each  side  to  keep  the 
bricks  apart  and  provide  a  joint  for  the  filler. 

It  is  claimed  for  the  rounded  edges  that  there  is 
no  tendency  for  the  corners  to  be  worn  or  chipped  off 
by  horses'  hoofs,  as  is  the  case  with  square  edges, 
leaving  the  bricks  rough  arid  the  joints  uneven.  But, 
on  the  other  hand,  it  is  maintained  by  the  advocates 
of  square-cornered  bricks  that  if  the  filling  of  the  joints 
is  properly  inserted  between  the  bricks,  and  if  of  suita- 


I 


Asphalt 
100 


Rectangular 

Wood  Block 

100 


/y^'iT  i  \ 


Granite 

Block 

150 


FlG.  58. 


ble  material,  no  such  tendency  will  exist  with  the  square  edges. 
It  would  seem  to  be  more  a  question  of  choice  rather  than 
positive  advantage  of  one  over  the  other.  Grooved  bricks  are 
supposed  to  have  the  advantage  of  retaining  more  of  the  filler 
that  goes  between  the  joints,  while  the  projections  on  the  sides 
of  other  forms  maintain  a  constant  distance  between  bricks,  and 
thus  permit  of  the  filler  being  inserted.  The  grooves  are  about 
one-eighth  inch  deep,  while  the  buttons  are  about  the  same 


198  HIGHWAY   ENGINEERING 

distance.  In  the  latter  case  it  is  very  questionable  practice, 
since  under  all  circumstances  joints  should  be  made  as  narrow 
as  possible.  Because  of  the  variability  in  the  character  of 
paving  bricks,  precautions  in  the  form  of  tests  have  been  uni- 
formly adopted  to  determine  the  quality  of  the  material  that 
is  being  offered.  Good  paving  bricks  should  be  hard,  tough, 
strong,  homogeneous,  impervious  to  water,  and  dense,  and  the 
following  tests  are  supposed  to  indicate  to  what  degree  the  brick 
possesses  these  qualities. 

Hardness.  This  quality  may  be  determined  by  the  ordinary 
hardness  test,  i.e.,  the  ease  with  which:  a  material  is  scratched  by 
certain  other  materials,  according  to  some  scale;  or  the  color  may 
be  taken  as  an  indicator,  though  the  latter  requires  experience 
and  judgment,  and  even  then  is  not  absolute.  The  hardness 
is  supposed  to  indicate  the  degree  with  which  the  material  will 
withstand  the  abrading  action  of  the  horses'  hoofs  and  wagon 
wheels;  and  an  average  hardness  of  six  in  Moh's  scale  is 
required. 

Moh's  Scale. 

1.  Talc,  common  laminated,  light-green  variety. 

2.  Gypsum,  crystallized  variety. 

3.  Calcite,  transparent  variety. 

4.  Fluorite,  crystalline  variety. 

5.  Apatite,  transparent  variety. 

6.  Orthoclase,  white  cleavable  variety. 

7.  Quartz,  transparent. 

8.  Topaz,  transparent. 

9.  Sapphire,  cleavable  variety. 
10.  Diamond. 

Toughness,  or  the  ability  to  resist  the  pounding  of  the  rapid 
blows  from  horses'  hoofs,  is  equally  important  with  the  forego- 
ing. These  two  characteristics  are  determined  by  what  is  known 
as  the  standard  Impact  and  Abrasion  Test. 


BRICK   PAVEMENTS  199 

Impact  and  Abrasion  Test.  "(1)  DIMENSIONS  MACHINE. 
The  standard  machine  shall  be  28  ins.  in  diameter  and  20  ins.  in 
length,  measured  inside  the  rattling  chamber.  Other  machines 
may  be  used  varying  in  diameter  between  26  ins.  and  30  ins.,  and 
in  length  from  18  ins.  to  24  ins. ;  but  if  this  is  done,  a  record  of  it 
must  be  attached  to  the  official  report.  The  rattler  may  be 
cut  up  into  sections  of  suitable  length  by  the  insertion  of  a,n 
iron  diaphragm  at  the  proper  point. 

"(2)  CONSTRUCTION  or  THE  MACHINE.  The  barrels  shall  be 
supported  on  trunnions  at  either  end.  In  no  case  shall  the  shaft 
pass  through  a  rattler  chamber.  The  cross-section  of  the  barrel 
shall  be  a  regular  polygon  having  14  sides.  The  head  staves 
shall  be  composed  of  gray  cast  iron,  not  chilled  or  case-hardened. 
There  shall  be  a  space  of  \  in.  between  the  staves  for  the  escape  of 
dust  and  small  pieces  of  waste.  Other  machines  may  be  used 
having  from  12  to  16  staves,  with  openings,  from  f  to  f  in.  be- 
tween staves;  but,  if  this  is  done,  a  record  of  it  must  be  attached 
to  the  official  report  of  the  test. 

"  (3)  COMPOSITION  OF  THE  CHARGE.  All  tests  must  be  executed 
on  charges  containing  but  one  make  of  brick  or  block  at  a  time. 
The  charge  shall  consist  of  9  paving  blocks  or  12  paving  bricks 
together  with  300  Ibs.  of  shot  made  of  ordinary  machinery  cast 
iron.  This  shot  shall  be  of  two  sizes,  as  described  below,  and  the 
shot  charge  shall  be  composed  of  }  (75  Ibs.)  of  the  larger  size  and 
f  (225  Ibs.)  of  the  smaller  size. 

"  (4)  SIZE  OF  SHOT.  The  larger  size  shall  weigh  about  7J 
Ibs.  and  be  about  2J  ins.  sq.  and  4J  ins.  long  with  slightly 
rounded  edges.  The  smaller  size  shall  be  cubes  of  1J  his.  on 
a  side,  with  rounded  edges.  The  individual  shot  shall  be  re- 
placed by  new  ones  when  they  have  lost  iV  of  their  original 
weight. 

"  (5)  REVOLUTIONS  OF  THE  CHARGE.  The  number  of  revolu- 
tions of  a  standard  test  shall  be  1,800  and  the  speed  of  rotation 
shall  not  fall  below  28  nor  exceed  30  per  minute.  The  belt  power 


200  HIGHWAY   ENGINEERING 

shall  be  sufficient  to  rotate  the  rattler  at  the  same  speed,  whether 
charged  or  not. 

"(6)  CONDITION  AND  CHARGE.  The  bricks  composing  the 
charge  shall  be  dry  and  clean,  and  as  nearly  as  may  be  possible 
in  the  condition  in  which  they  were  drawn  from  the  kiln. 

"  (7)  CALCULATION  OF  THE  RESULTS.  The  loss  shall  be  calcu- 
lated in  the  per  cents  of  weight  of  the  dry  brick  composing  the 
charge,  and  no  result  shall  be  considered  as  official  unless  it  is 
the  average  of  two  distinct  and  complete  tests  made  on  separate 
charges  of  brick." 

Strength  or  Transverse  Strength,  a  characteristic  which 
every  brick  should  possess  so  that  it  may  be  able  to  withstand 
the  tendency  to  break  which  arises  when  the  brick  is  unevenly 
supported  on  the  foundation. 

The  following  is  the  standard  method  adopted  for  this  test : 

"  1.  Support  the  brick  on  edge,  or  as  laid  in  a  pavement,  on  a 
hardened-steel  knife  rounded  longitudinally  to  the  radius  of  12 
ins.,  and  transversely  to  the  radius  of  £  in.,  and  bolted  in  position 
so  that  the  screw-span  of  6  ins.  applied  to  load  in  the  middle  of 
the  top  shall  pass  through  the  steel  knife-edge,  straight,  longi- 
tudinally, and  rounded  transversely  to  a  radius  of  yV  in. 

"2.  Apply  the  load  to  the  middle  of  the  top  face  through  a 
hardened-steel  knife-edge,  straight,  longitudinally,  and  rounded 
transversely  to  a  radius  of  one-sixteenth  inch. 

"3.  Apply  the  load  in  a  uniform  rate  of  increase  until  fracture 
ensues. 

"  4.  Compute    the    modulus    of    rupture    by    the    formula 

3WL 


F  = 


2BD 


in  which  F  =  modulus  of  rupture  in  pounds  per  square  inch; 
W=the  total  brick  load  hi  pounds;  L=the  length  of  span  in 
inches,  six:  B  =  breadth  of  brick  in  inches;  D  =  depth  of  brick 
in  inches. 


BRICK   PAVEMENTS  201 

"5.  Samples  for  test  must  be  free  from  all  visible  irregulari- 
ties of  surface  or  deformities  in  shape,  and  their  upper  and  lower 
faces  must  be  practically  parallel. 

"  6.  Not  less  than  ten  bricks  shall  be  broken,  and  the  average 
of  all  is  to  be  taken  for  the  standard  test." 

"  Cross-breaking  test  of  paving  brick  is  made  for  the  following 
reasons : 

"  1.  It  furnishes  the  means  of  comparing  the  differences  of 
various  kinds  of  clay  paving  material. 

"  2.  For  any  particular  kind  of  brick  it  shows  whether  the 
brick  has  been  properly  treated  in  the  various  stages  of  its 
manufacture. 

"3.  It  indicates  the  resistance  of  the  material  in  cross- 
breaking  when  laid  on  beds  of  unyielding  and  uneven  surface. 

"  4.  The  cross-section  being  exposed,  the  interior  structure 
may  be  examined." 

The  Crushing  Strength  of  a  brick  is  usually  determined  by 
taking  one-half  of  the  specimen  that  has  been  broken  in  the 
transverse  test.  This  piece  is  placed  upon  the  horizontal  plat- 
form of  the  testing  machine,  and  another  parallel  surface  of  steel 
held  in  the  cross-heads  of  the  machine  is  made  to  gradually  ap- 
proach. The  power  is  kept  constant  so  that  the  pressure  applied 
increases  until  failure  results.  The  total  load  applied  to  the  speci- 
men, divided  by  the  measured  horizontal  area  of  the  brick,  will 
give  the  pounds  per  square  inch  that  the  material  will  with- 
stand. To  secure  even-bearing  surfaces,  and  hence  prevent  any 
inequality  of  bearing,  blotting  paper  or  pieces  of  leather  are  usual- 
ly placed  next  to  the  surfaces  of  the  brick.  This  secures  an  even 
distribution  of  the  pressure. 

Homogeneity.  Each  brick,  taken  as  a  unit,  should  be  homo- 
geneous in  character  to  insure  a  uniform  wear.  If  part  of  a 
brick  is  properly  burned  and  the  rest  improperly  burned,  the 
former  will  resist  the  wear  to  a  much  greater  extent  than  the 
latter,  resulting  in  an  unevenly  worn  brick.  Each  brick,  there- 


202  HIGHWAY   ENGINEERING 

fore,  should  be  perfectly  and  completely  fused  to  secure  a  homo- 
geneous unit. 

Uniformity.  This  refers  to  all  the  bricks  that  may  be  used 
in  one  contract.  It  is  required  that  the  material  itself  shall  be 
uniform,  that  the  method  of  manufacture  shall  be  identical, 
and  that  the  resultant  product  shall  be  uniform  in  character. 
The  purpose  of  this  is  that  the  pavement  may  wear  evenly,  as 
under  such  conditions  the  best  results  obtain.  It  is  much  better 
to  lay  a  pavement  of  bricks  that  are  uniformly  soft  in  character 
than  to  construct  one  of  bricks  alternately  hard  and  soft,  which 
results  in  an  uneven  surface  in  a  short  time. 

Imperviousness.  All  material  for  paving  should  be  imper- 
vious, as  otherwise  it  absorbs  moisture  and  tends  to  disintegrate. 
A  good  brick  should  absorb  no  more  than  two  per  cent  of  moist- 
ure. It  is  not  an  important  test,  however,  and  not  recom- 
mended as  one  to  indicate  the  quality  of  a  brick,  as  the  results 
are  misleading. 

Density,  or  the  specific  gravity  of  a  brick,  is  determined  to 
indicate  the  relative  amount  of  material  in  the  specimens  sub- 
jected to  test.  Other  things  being  equal,  the  denser  specimen, 
i.e.,  the  one  with  the  greatest  amount  of  material,  should  wear 
the  longest. 

Sp.Gr.  =  A  ^  ; 

A  =  weight  of  brick  in  air ; 
B  =  weight  of  brick  in  air  saturated; 
C  =  weight  of  brick  in  water ; 
average  from  1.90  to  2.60. 

FOUNDATION 

Without  a  properly  laid  foundation  irregularities  quickly 
appear  with  consequent  increased  wear  and  tear  to  pavement  and 
vehicles,  together  with  an  increase  in  the  tractive  force.  The 
object  to  be  attained  with  any  foundation  is  to  support  the  over- 


BRICK   PAVEMENTS  203 

lying  covering,  and  particularly  where  brick  is  used  must  the  top 
surface  be  maintained  smooth  and  even. 

Various  forms  of  foundation  have  been  employed  upon  which 
to  place  the  brick,  but  there  is  no  question  but  that  the  most 
satisfactory  one  is  of  concrete.  Sand  and  gravel  are  not  at  all 
desirable.  When  either  is  employed,  however,  about  8  ins.  is 
laid  on  the  prepared  subgrade,  and  carefully  rolled  with  a  10  ton 
roller  to  procure  consolidation.  A  cushion  coat  of  sand  2  ins. 
in  depth  is  placed  beneath  the  brick,  and  a  templet  passed  over 
it  to  shape  the  surface  parallel  to  that  of  the  pavement. 

Sand  alone  as  a  foundation  is  pretty  poor,  as  the  wear  becomes 
abnormal.  It  may  be  used,  however,  in  connection  with  plank- 
ing as  a  foundation,  and  with  fairly  satisfactory  results.  Under 
these  conditions  the  sand  is  first  laid  to  a  depth  of  about  3  ins., 
and  upon  this  are  placed  treated  boards,  1  in.  to  2  ins.  thick,  while 
on  top  of  these  again,  a  1  to  2  in.  cushion  coat  of  sand  is  spread 
to  receive  the  brick.  The  object  of  the  cushion  coat  is  to  secure 
an  equal  bearing  for  all  points  of  the  under  surface  of  the  bricks, 
and  this  result  is  achieved  through  the  fact  that  the  sand  con- 
forms to  the  irregularities  of  the  bottom  surface.  Such  a  founda- 
tion is  only  suitable  to  light  traffic. 

Another  form  employed  where  brick  is  cheap  is  a  bottom 
layer  of  brick,  laid  flat  on  a  bed  of  sand,  which  is  rolled  and 
rammed,  brought  to  an  even  surface,  and  covered  with  a  cushion 
coat  of  one  inch  or  two  inches  to  receive  a  top  layer,  set  on  edge. 
This  is  a  quite  common  practice  in  the  Middle  West,  where  a  stone 
foundation  would  be  too  expensive. 

Where  broken  stone  is  used  as  the  foundation,  it  is  prepared 
by  rolling  until  it  has  become  well  compacted  and  firm.  Upon  it 
is  then  placed  the  usual  cushion  coat,  and  above  this  the  brick. 
The  broken  stone  should  be  so  well  rolled  and  compacted  that 
there  is  no  danger  of  the  sand  of  the  cushion  coat  filtering  into  its 
interstices  and  leaving  voids  beneath  the  brick. 

Concrete  is  without  doubt  the  best  foundation  for  brick,  as  it 


204  HIGHWAY   ENGINEERING 

is  for  every  other  pavement.  The  same  conditions  obtain  here 
as  for  any  other  foundation  of  the  same  material.  The  only 
drawback  to  concrete  is  its  expense,  particularly  where,  as  in 
some  localities,  stone  of  the  proper  character  is  scarce.  The 
upper  surface  of  the  concrete  should  be  smoothed  off  as  much  as 
possible  when  laid,  and  when  set,  the  cushion  coat  of  sand  should 
be  laid  on  top  of  it  to  take  up  any  irregularities  either  in  the 
foundation  or  the  brick,  and  thus  secure  an  even  bearing. 

JOINT   FILLING 

The  purpose  of  the  joint  filling  is  to  secure  a  watertight  sur- 
facing. Many  materials  have  been  used  with  varying  success, 
but  the  more  popular  and  common  are  cement  grout  and  paving 
cement. 

This  cement-grout  filler  is  composed  of  one  part  cement  and 
one  part  sand,  or  of  neat  cement  alone.  When  the  former  is 
used,  the  sand  and  cement  are  thoroughly  mixed  dry,  and  water 
then  added  till  the  proper  consistency  is  reached.  The  grout  is 
applied  by  spreading  it  over  the  pavement,  and  sweeping  it  into 
the  joints  until  it  appears  flush  with  the  upper  edges  of  the  brick, 
while  upon  this  is  spread  a  thin  surfacing  of  fine  sand.  During 
this  part  of  the  construction  and  until  the  cement  has  set  traffic 
is  excluded  from  the  thoroughfare. 

The  principal  advantages  of  such  a  filler  are  that  it  is  watertight 
and,  furthermore,  being  hard  and  tough,  resists  the  wear  and  tear 
of  traffic  to  an  equal  extent  with  the  brick,  thus  preventing  their 
edges  from  chipping,  which  is  not  the  case  with  other  forms  of 
joints.  Its  disadvantage  is  that  it  in  no  way  provides  for  the 
expansion  of  the  pavement  in  hot  weather,  in  consequence  of 
which  rumbling  may  be  caused  due  to  the  fact  that  the  brick 
draws  away  from  the  foundation,  leaving  a  hollow  space  between. 

To  overcome  this,  however,  expansion  joints  may  be  placed  at 
intervals,  both  longitudinally  and  transversely,  along  the  pave- 
ment. Such  joints  consist  of  either  tar  or  asphalt,  are  from  J 


BRICK   PAVEMENTS  205 

in.  to  1  in.  wide,  and  are  placed  next  each  curb  to  take  up  the 
expansion  due  to  rise  in  temperature.  Transversely  the  joints 
are  spaced  about  40  to  60  ft.  apart,  or  else  the  expansion  is  al- 
lowed for  by  filling  2  or  3  consecutive  joints  at  stated  intervals 
with  the  prescribed  mixture. 

Tar  filler  has  some  of  the  advantages  of  the  cement  grout, 
besides  others  of  its  own,  but  its  disadvantages  are  more  serious 
than  the  latter.  Such  a  filler  produces  a  watertight  joint,  and 
allows  for  the  expansion  of  the  pavement  in  hot  weather; 
but,  on  the  other  hand,  it  is  too  soft  to  protect  the  edges  of  the 
brick  from  chipping,  in  extreme  warm  weather  it  melts  and  runs, 
while  in  cold  weather  it  becomes  brittle  and  is  easily  chipped  into 
fragments,  to  be  removed  by  one  means  or  another. 

The  tar  used  is  a  No.  5  or  No.  6  coal-tar  distillate,  while 
asphalt  may  be  added  or  used  alone  to  secure  a  filler  not  so  easily 
affected  by  temperature.  It  is  applied  hot,  being  poured  into  the 
joints  until  it  appears  flush  with  the  surface,  and  on  top  of  this 
spread  the  usual  coat  of  sand  which  is  worked  hi  to  the  j  obits  by 
brooming  and  later  by  traffic. 

Sand  as  a  filler  is  often  used,  but  as  it  possesses  the  disad- 
vantage of  allowing  water  to  percolate  through  to  the  foundation, 
it  is  not  entirely  satisfactory.  Where  it  is  used,  it  should  be 
perfectly  dry  and  fine,  and  when  applied  to  the  pavement  should 
be  well  broomed  into  the  joints  with  enough  left  on  the  surface, 
about  one-half  inch,  for  traffic  to  continue  the  operation. 

LAYING   THE   BRICK 

After  the  foundation  has  been  properly  prepared,  a  cushion 
coat  of  sand  one  inch  to  two  inches  deep  is  spread  uniformly  over 
it,  and  to  secure  the  proper  crown  a  wooden  templet  is  moved 
over  the  sand  from  one  end  of  the  section  to  be  paved  to  the 
other.  This  templet  is  constructed  of  several  pieces  of  board 
with  the  under  surface  conforming  in  outline  to  the  desired  trans- 
verse grade.  If  the  street  is  comparatively  narrow,  the  templet 


206  HIGHWAY   ENGINEERING 

is  built  for  the  entire  cross-section,  the  ends  rest  upon  the  curbs, 
and  the  whole  is  drawn  along  over  the  sand.  Where  the  street  is 
wide,  however,  a  templet  is  built  for  the  one-half  section,  and  is 
used  by  resting  one  end  on  the  curb  and  the  other  on  a  strip  of 
lumber  placed  along  the  centre  of  the  street. 

In  laying  the  brick  the  precaution  is  always  taken  to  leave 
the  sand  undisturbed,  and  to  accomplish  this  the  pavers  stand  or 
kneel  only  on  those  bricks  that  have  already  been  laid.  Each 
course  is  started  at  the  curbs  so  that  it  shall  break  joints  with  the 
two  adjacent  courses,  and  when  a  course  has  been  completed  it  is 
keyed  up  with  an  iron  bar  so  that  the  last  brick  may  be  inserted. 
The  courses  should  be  kept  perpendicular  to  the  axis  of  the  street, 
to  accomplish  which  they  are  "  trued  up  "  every  four  or  five  feet. 

After  laying,  the  pavement  is  rolled  with  a  steam  roller  until 
the  bricks  have  reached  an  even-bearing  surface  and  no  longer 
move  under  the  action  .of  the  roller.  Or,  if  this  is  not  feasible, 
planks  are  laid  parallel  to  the  curb  and  rammed  by  a  heavy  ram- 
mer. It  is  not  advisable  to  lay  the  plank  across  the  street  and 
ram,  as  it  is  then  likely  to  cause  an  uneven  settlement. 

While  it  is  the  more  usual  custom  to  lay  the  brick  in  lines 
perpendicular  to  the  axis  of  the  street,  they  are  sometimes  ar- 
ranged herringbone  fashion.  There  is  no  particular  advantage  in 
this  except  that  in  the  street  itself  no  joints  are  parallel  to  the  line 
of  traffic,  while  it  has  a  decided  disadvantage  since  "  between  the 
streets  it  brings  the  line  of  cross  joints  lengthwise  to  the  travel  of 
the  street,  which  permits  a  weak  spot  in  the  pavement,  and  at 
intersections  it  brings  a  great  many  of  the  bricks  lengthwise  of 
the  traffic  turning  the  corners." 

INTERSECTIONS 

The  following  figures  (Figs.  58  and  59)  show  two  methods  of 
laying  brick  at  the  intersection  of  streets,  the  general  purpose  of 
which  forms  of  construction  is  to  reduce  the  wear  and  afford  at  all 
points  a  good  foothold. 


BRICK   PAVEMENTS 


207 


In  Fig.  .58,  wagons  turning  from  one  street  to  another  follow 
a  line  which  is  at  all  points  approximately  perpendicular  to  the 
length  of  the  brick,  which  is  the  best  condition  for  both  wear  and 
foothold,  while  when  crossing  the  street  in  a  straight  line,  the 
direction  of  traffic  is  diagonal  to  the  length  of  brick;  and  which, 


FIG.  58. 

in  the  opinion  of  some,  is  supposed  to  be  a  condition  superior  to 
any  other. 

Few  wagons  will  travel  along  the  courses  of  the  bricks  and 
none  for  any  considerable  distance,  which  is  the  most  objection- 
able direction  as  regards  uniformity  of  wear.  The  weak  lines  are 
at  the  junctions  of  the  four  rectangles  which  are  in  the  middle 
of  the  streets.  These  can  be  laid  so  carefully  and  with  such  good 
foundation  that  they  will  give  no  trouble.  Careless  laying  will 
cause  unequal  settlement,  which  will  have  greater  effect  along 


208 


HIGHWAY   ENGINEERING 


these  lines  than  in  the  regularly  laid  pavement.     Special  care 
should,  therefore,  be  taken  at  intersections. 

Fig.  59  shows  another  method  of  placing  the  brick  at 
intersections,  which  is  more  easily  laid  than  the  other;  besides 
which  careless  workmanship  has  not  nearly  so  great  an  effect 


FIG.  59. 

upon  it.  With  good  labor  the  former  is  the  superior,  because 
in  the  latter  under  two  conditions  traffic  is  travelling  along 
the  length  of  the  brick  in  turning  corners,  thus  causing  un- 
equal wear. 

The  following  "  Directions  for  Laying  Vitrified  Brick  Street 
Pavements"  indorsed  and  recommended  by  the  National  Paving 
Brick  Manufacturers'  Association,  contains  such  valuable  mate- 
rial that  it  is  submitted  in  full. 


BRICK   PAVEMENTS  209 

"DIRECTIONS    FOR    LAYING    VITRIFIED    BRICK 
STREET    PAVEMENTS" 

Form  Two.     Specification  One.     Best  Known  Construction — 
Concrete  Base  Cement  Filler 

SECTION  1.  SUBSTRUCTURE  OR  GRADING. — Earth  in  excava- 
tion to  be  removed  with  plough  and  scraper,  or  other  device,  to 
within  two  (2)  inches  of  subgrade,  then  brought  to  the  true 
grade  with  the  roller,  the  weight  of  which  should  be  not  less  than 
five  (5)  nor  more  than  eight  (8)  tons.  If  the  earth  is  too  hard  to 
receive  compression  through  the  roller,  then  loosen  the  remaining 
inches  with  a  pick  and  cart  away. 

Earth  in  embankment  must  be  applied  in  layers  of  eight  (8) 
inches  in  thickness  and  each  layer  thoroughly  rolled,  and  in  both 
excavation  and  embankment  the  subgrade  must  have  a  uniform 
density. 

If  the  underground  is  spouty  clay,  tile  drainage  should  be  pro- 
vided to  carry  off  this  accumulation  of  wet. 

REASONS   WHY 

The  attempt  to  remove  earth  to  the  proper  depth  or  grade 
line  with  plough  and  scraper  is  usually  fatal  to  the  general  surface 
of  the  subgrade,  for  the  reason  that  no  man  can  hold  a  plough,  or 
team  draw  the  same  to  a  straight  grade ;  therefore  in  an  attempt 
to  get  too  close  to  subgrade  with  a  plough,  holes  will  be  gouged 
below  the  true  grade.  When  the  shovellers  commence  the  re- 
moval of  the  ploughed  earth,  they  will  invariably  sink  these  same 
low  places  still  lower,  and  when  the  finishing  begins  these  low 
places  will  necessarily  have  to  be  filled  and  compacted  with  the 
roller.  Then  you  have  different  characters  of  solidity,  which  are 
objectionable  and  detrimental  to  good  work. 

The  prime  reason  for  not  using  a  roller  weighing  more  than 
eight  (8)  tons  is  that  they  are  too  cumbersome  and  unwieldy  and 
very  slow  moving,  while  with  a  lighter  and  quicker  moving  one 
14 


210  HIGHWAY   ENGINEERING 

you  pass  many  times  over  the  subgrade  and  get  better  results 
in  having  your  subgrade  more  uniformly  compacted. 

The  filling  with  loose  earth  of  portions  of  the  work  that  is 
below  grade  will  be  found  necessary  very  often  if  an  attempt 
is  made  to  plough  too  close  to  the  grade  line,  then  the  lighter 
roller  is  found  more  effective  in  bringing  such  places  to  the 
same  density  as  the  undisturbed  portion. 

When  embankment  is  necessary  to  bring  the  street  to  the 
required  grade  line,  it  is  very  obvious  that  the  earth  should  be 
deposited  in  equal  layers  of  not  more  than  eight  (8)  inches  thick, 
and  each  layer  thoroughly  rolled.  A  six  or  eight  ton,  or  even 
a  heavier  roller,  will  have  little  effect  in  compression  below 
eight  inches,  and  all  embankments  should  be  compacted  as  thor- 
oughly as  possible  before  applying  the  superstructure;  for  earth 
once  disturbed  and  removed  from  its  natural  bed  takes  a  long 
time  to  acquire  its  original  solidity,  the  scientific  reason  for 
which  would  take  too  much  space  and  time  to  enter  upon  here. 

Underdrainage  is  not  absolutely  essential,  but  in  wet  and 
spouty  understratum  much  is  added  to  the  durability  of  the 
structure  by  keeping  the  subfoundation  dry,  and  under  forego- 
ing wet  conditions  underdrainage  is  the  only  way  to  accom- 
plish the  best  results 

SECTION  2. — CURBING. — Stone  curbing  should  all  be  hauled 
and  distributed  and  set  before  the  grading  is  finished,  and  may 
then  be  used  as  a  guide  to  finish  the  subgrade. 

It  should  range  in  thickness  from  four  (4)  to  six  (6)  inches, 
twenty  (20)  to  thirty-six  (36)  inches  wide,  the  business  and 
street  traffic  governing  the  same.,  and  lengths  not  shorter  than 
four  (4)  feet,  except  at  closures,  neatly  dressed  on  top  with  a 
square  or  rounded  edge,  and  four  (4)  inches  down  on  the  inside. 
The  outer  surface  to  be  tool-dressed  to  the  depth  of  the  face  ex- 
posed and  to  the  depth  of  the  thickness  of  the  brick  and  sand 
cushion.  If  cement  concrete  curb  is  used,  it  should  be  com- 
pleted before  the  work  of  finishing  the  subgrade  begins. 


BRICK   PAVEMENTS  211 

Curb  corners  of  streets  and  alleys  shouk.  be  made  circular. 

EXTRA   MENTION 

If  concrete  curb  and  gutter  is  used,  it  must  be  placed  in 
position  before  any  of  the  other  work  is  commenced,  except, 
possibly,  some  of  the  heavier  grading,  and  it  is  essential,  if 
natural  stone  curb  is  used,  to  have  it  all  in  place  before  any 
portion  of  the  grading  is  finished,  for  the  reason  that,  after  you 
have  finished  a  subgrade  and  given  it  the  proper  contour  and 
surface  it  should  never  be  disturbed  by  unnecessary  wheelage, 
and  nothing  destroys  it  so  effectually  as  hauling  heavy  stone 
curb  over  it;  and  in  renewing  these  broken  places  they  are  rare- 
ly returned  to  the  original  conditions. 

The  curb  should  all  be  set  before  the  finishing  of  the  sub- 
grade  begins,  if  for  no  other  reason  than  that  it  affords  the 
very  best  guide  for  the  said  finishing. 

MARGINAL  CURB 

SECTION  3. — MARGINAL  CURB. — Should  always  be  of  a  hard 
and  durable  character  of  stone,  and  from  fourteen  (14)  to  eighteen 
(18)  inches  deep,  dressed  on  top,  and  five  (5)  inches  down  on  the 
face  next  to  the  brick,  set  accurately  to  fit  the  curvature  of  the 
cross-section  of  the  street  on  six  (6)  inches  of  concrete  and 
backed  up  with  the  same  within  six  (6)  inches  of  the  top. 

EXTRA  MENTION 

Marginal  curb  should  always  be  of  a  hard  and  durable 
character  of  stone  (hard  wood  is  better  than  soft  stone),  and 
set  on  and  backed  up  with  a  good  Portland-cement  concrete, 
mixed  in  the  proportion  of  1  to  2  to  4. 

Marginal  curb  is,  as  a  rule,  used  to  sustain  a  paved  street 
against  one  that  is  unpaved;  therefore  the  reason  it  should  be 
well  and  properly  set,  and  unless  it  is,  the  impact  of  the  wheelage 


212  HIGHWAY   ENGINEERING 

in  passing  from  the  unpaved  to  the  paved  street  will  soon  drive 
it  down  and  loosen  it  if  not  firmly  and  securely  set,  and  in  a 
short  time  the  pavement  begins  to  break  and  give  way  and  will 
continue  to  do  so  for  quite  a  distance  into  the  intersection. 

Even  with  the  marginal  curb  set  in  the  above  manner  there 
should  be  a  margin  of  crushed  stone  or  clean  gravel  to  the  width 
of  three  or  four  feet  and  eight  (8)  or  ten  (10)  inches  deep  spanning 
the  width  of  the  opposing  unpaved  street  and  tamped  firmly 
against  the  marginal  curb.  With  these  precautions  you  will 
avoid  the  rapid  destruction  of  the  margin  of  your  paved  streets. 

SECTION  4. — CONCRETE  FOUNDATION. — Should  be  of  approved 
quality  of  hard  rock,  free  from  all  refuse  and  foreign  matter,  with 
no  fragment  larger  than  will  pass  through  a  two  (2)  inch  ring,  and 
no  smaller  than  will  pass  though  a  one  (1)  inch  ring  in  their 
longest  dimensions. 

Clean,  sharp,  dry  sand  thoroughly  mixed  in  its  dry  state 
with  an  approved  brand  of  either  hydraulic  or  Portland  ce- 
ment until  the  whole  mass  shows  an  even  shade.  If  hydraulic, 
the  proportion  of  mixture  should  be  1  part  of  cement  and  2 
parts  of  sand.  If  of  Portland,  1  part  of  cement  to  3  parts 
of  sand. 

To  the  above  mixture  should  be  added  sufficient  clean 
water  to  mix  to  a  plastic  mass,  fluid  enough  to  rapidly  sub- 
side when  attempted  to  heap  into  a  cone  shape.  To  this  mixture 
add  four  (4)  and  six  (6)  parts,  respectively,  of  damp  crushed  stone, 
or  good  gravel  carrying  sufficient  sand  to  make  the  mixture,  and 
then  turn  the  whole  mass  over  not  less  than  three  (3)  times,  or 
until  every  fragment  is  thoroughly  coated  with  the  cement  mix- 
ture. For  the  reception  of  this  mixture,  the  grade  should 
be  set  off  in  five  foot  squares,  with  a  stake  at  each  corner.  Tops 
of  each  should  be  at  the  surface  of  concrete,  which  must  be 
tamped  until  free  mortar  appears  on  the  surface.  Occasional 
sprinkling  in  extra  hot,  dry  weather  is  beneficial.  After  thirty- 
six  hours  the  cushion  sand  may  be  spread. 


BRICK   PAVEMENTS  213 


EXTRA  MENTION 

If  the  combination  of  gravel  and  sand  is  used  the  mixture  for 
natural  cement  should  be  one  (1)  measure  of  cement  to  six  (6) 
measures  of  the  mixture.  If  Portland  cement,  one  (1)  meas- 
ure of  cement  to  eight  (8)  measures  of  the  mixture. 

There  is  but  one  way  to  make  good  cement  mixtures,  pre- 
suming, of  course,  you  have  good  material,  and  that  is  to 
thoroughly  mix  the  dry  materials.  It  is  essential  that  the  sand 
and  cement  should  be  thoroughly  incorporated  in  their  dry  state ; 
if  not  then  it  can't  be  done  after  the  water  is  applied.  In  the 
first,  you  will  have  a  homogeneous  mass;  in  the  second,  a 
heterogeneous.  In  the  one  your  mixture  is  complete  and  your 
structure  is  uniform;  in  the  other,  it  varies  and  your  structure 
is  uncertain.  The  above  applies  especially  to  platform  mixing. 
In  machine  manipulation  the  dry  mixing  isn't  so  readily  obtain- 
able, but  could  be  more  nearly  approached  if  greater  care  were 
taken.  Thorough  mixing  in  both  dry  and  wet  state,  with  good 
material  and  proper  proportions,  insures  a  good  concrete,  whether 
it  be  of  crushed  stone  or  gravel. 

SECTION  5. — SAND  CUSHION. — Sand  should  be  clean  and  free 
from  foreign  or  loamy  matter.  It  need  not  necessarily  be  sharp. 
It  should  be  two  (2)  inches  thick  before  the  compression  of  the 
brick  by  rolling.  The  sand  should  be  spread  by  the  aid  of  a  tem- 
plate the  whole  or  one-half  the  width  of  the  street,  and  made  to 
conform  with  the  true  curvature  of  the  street  cross-section. 

EXTRA  MENTION 

The  preparation  of  the  subgrade  having  been,  with  care, 
brought  to  a  true  plane  as  to  curvature  and  grade,  and  to  a 
uniform  thickness,  the  work  is  ready  for  the  cushion  for  the 
brick,  for  which  any  good  clean  sand  may  be  used,  whether  it 
be  sharp  or  spherical ;  but  it  is  next  to  the  impossible  to  spread 
it  satisfactorily  with  a  template  or  in  any  other  manner  when 


214  HIGHWAY   ENGINEERING 

it  is  wet,  and  if  you  insist  on  your  pavement  maintaining  its 
symmetrical  form  the  sand  must  be  evenly  spread;  and  there 
is  but  one  method  for  doing  this,  and  that  is  mechanically,  by 
the  aid  of  a  template,  formed  to  fit  the  curvature  of  the  street 
and  armed  with  small  metal  wheels  at  either  end,  rolling  on  the 
curb  at  one  end  and  on  a  4x4  in.  scantling  laid  lengthwise 
through  the  centre  of  the  street  at  the  other. 

If  the  roadway  of  the  street  isn't  to  exceed  twenty-five  (25) 
feet  in  width  or  less,  the  template  can  be  made  to  span  the  entire 
width,  both  ends  rolling  on  the  curb. 

This  manner  insures  an  even  thickness  of  sand  over  the 
surface  of  the  concrete,  giving  to  each  individual  brick  a  like 
thickness  of  cushion,  so  that  when  the  brick  surface  is  rolled 
each  brick  will  present  the  same  resistance  to  the  pressure  of 
the  roller,  and  you  will  then  perforce  have  a  smooth  surface; 
otherwise,  if  the  sand  is  of  uneven  thickness  the  tendency  of 
those  bricks  resting  on  the  thicker  bed  of  sand  is  to  sink,  under 
the  pressure  of  the  roller,  lower  than  those  resting  on  a  thinner 
layer,  and  the  result  is  an  undulating  and  uneven  surface. 

BRICK 

SECTION  6. — BRICK.  The  brick  should  all  be  hauled  and  neatly 
piled  within  the  curb  line  before  the  grading  is  finished,  or,  if  al- 
lowed by  the  engineer,  delivered  in  wagons  and  carried  from  the 
pile  or  wagon  on  pallets  with  clamps — not  wheeled  with  barrows. 
In  hauling  from  car  no  throwing  or  dumping  is  allowed.  They 
should  be  first-class  and  thoroughly  vitrified,  showing  at  least 
one  fairly  straight  face;  if  the  edges  are  rounded  the  radius 
should  not  be  greater  than  -f$  of  an  inch.  They  should  not 
be  less  than  2}  X4X8,  or  more  than  3ix4x9i  ins.,  free 
from  cracks,  with  but  slight  lamination,  and  at  least  1  edge 
with  but  slight  kiln  marks  allowed,  and  should  stand  the  tests 
promulgated  by  the  National  Brick  Makers'  Association. 


BRICK   PAVEMENTS  215 

EXTRA  MENTION 

It  is  not  only  good  practice  to  have  all  of  the  brick  hauled 
and  distributed  just  inside  the  curb  line  before  the  work  of 
grading  begins  on  any  street  block,  but  it  is  economy,  as  ex- 
perience has  taught  us  that  it  is  very  expensive  to  attempt  to 
get  brick  into  a  block  after  the  other  work  has  begun.  Each 
side  of  the  street  should  have  the  required  number  of  brick 
neatly  ricked  up  to  lay  to  the  centre  of  the  street,  thereby  always 
maintaining  the  minimum  distance  to  carry  the  brick  to  the 
setter. 

In  order  to  get  the  brick  to  the  setter  with  the  least  possible 
abrasion  or  injury  to  the  same,  it  is  best  to  carry  them  on 
pallets,  and  so  deposit  them  that  the  person  laying  them  in  the 
street  will  deposit  them  perfect  edge  up.  No  wheeling  or  team- 
ing should  be  permitted  over  the  brick  at  any  stage  prior  to 
opening  the  same  to  the  public. 

BRICK-LAYING 

SECTION  7. — BRICK-LAYING.  Brick  may  be  laid  either  at  a 
right  angle  or  an  angle  of  forty-five  degrees  to  the  curb,  as  the 
engineer  may  direct,  and  in  either  way  the  line  or  course  of  brick 
must  be  kept  straight  or  within  a  maximum  variation  of  two 
inches ;  if  greater  than  that,  as  many  courses  as  necessary  should 
be  taken  up  and  relaid  until  the  defect  in  alignment  is  removed. 

No  parts  of  brick  should  be  allowed  in  the  pavement  ex- 
cept the  beginning  or  ending  of  courses  or  other  closures.  The 
brick  must  be  laid  with  the  best  edges  exposed  as  near  in  con- 
tact as  possible;  they  must  be  closely  inspected  before  laying 
and  also  after  laying  and  after  rolling.  All  soft  brick,  and  those 
badly  spalled  or  ill-shapen,  must  be  removed  and  replaced  with 
perfect  ones.  The  kiln-marked  ones  may  be  turned  over,  and 
if  the  reverse  edge  is  smooth  and  no  other  faults  be  found,  they 
can  remain  in  the  pavement. 


216  HIGHWAY   ENGINEERING 

EXTRA  MENTION 

As  to  the  alignment  of  the  courses  of  the  brick  there  is  but 
little  choice,  either  way  is  admissible  without  comment.  The 
brick  should  be  as  nearly  in  contact  as  it  is  possible  to  lay  them, 
for  when  the  rolling  is  in  progress,  if  there  is  appreciable 
space  between  the  brick  in  the  compression  and  bedding  into 
the  cushion  sand,  the  brick  will  have  a  tendency  to  rock,  and 
instead  of  receiving  a  flat  foundation,  as  they  should,  it  will  be 
in  a  curved  form,  made  by  the  rocking  of  the  brick  as  the  roller 
passes  on  and  off  them,  and  the  pavement  will  require  more 
grout  to  fill  the  interstices. 

It  isn't  bad  practice,  if  the  gutter  gradient  is  very  flat,  to 
lay  five  or  six  longitudinal  courses  parallel  with  the  curb  as 
there  will  be  less  hindrance  to  the  gutter  drainage. 

SECTION  8. — ROLLING  AND  TAMPING.  After  the  brick  in  the 
pavement  are  inspected  and  the  surface  is  swept  clean  of  spalls, 
they  must  be  well  rolled  with  a  five  (5)  ton  steam  roller  in  the 
following  manner:  The  brick  next  the  curb  should  be  tamped 
with  a  hand  wood  tamper  to  the  proper  gutter  grade.  The  rolling 
will  then  commence  near  the  curb  at  a  very  slow  pace  and  con- 
tinue back  and  forth  until  the  centre  of  the  pavement  is  reached, 
then  pass  to  the  opposite  curb  and  repeat  in  the  same  manner  to 
the  centre  of  the  street.  After  this  first  passage  of  the  roller  the 
pace  may  be  quickened  and  the  rolling  continued  until  each 
brick  is  firmly  embedded  in  the  sand  cushion.  The  roller  shall 
then  be  started  at  the  end  of  the  block  and  the  pavement  rolled  trans- 
versely at  an  angle  of  forty-five  degrees  to  curb,  repeat  the  rolling  in 
like  manner  in  the  opposite  direction.  Before  this  transverse  roll- 
ing takes  place  all  broken  or  injured  brick  must  be  taken  up  and 
replaced  with  perfect  ones. 

EXTRA  MENTION 

There  is  no  question  open  to  discussion  as  to  the  virtue  of 
a  steam  roller  on  a  brick  pavement.  It  is  very  necessary  in 


BRICK   PAVEMENTS  217 

order  to  give  it  a  smooth  surface.  The  transverse  rolling  is 
very  necessary  in  order  to  remove  the  slight  wavy  condition  of 
the  surface  extending  laterally  from  curb  to  curb,  which  will 
occur  after  the  longitudinal  rolling,  and  is  the  result  of  the 
thrust  or  impact  occasioned  by  the  propelling  power  of  the 
roller.  If  the  roller  was  drawn  instead  of  being  propelled  these 
apparent  waves  would  not  occur.  Therefore,  the  transverse  roll- 
ing will  practically  remove  them.  The  longitudinal  rolling  should 
always  be  from  curb  toward  the  centre.  The  curved  transverse 
section  of  the  street  has  a  tendency  to  move  the  brick  endwise 
toward  the  curb;  therefore,  under  the  pressure  of  the  roller,  if 
you  start  the  roller  in  the  middle  and  roll  toward  the  curb  the 
gutter  bricks  that  you  have  previously  tamped  to  grade  will 
be  very  much  disturbed  and  your  flow  line  will  require  re- 
tamping.  If  it  were  practicable  to  use  the  roller  absolutely 
against  the  curb  the  rolling  might  be  done  from  the  centre 
to  the  curb. 

SECTION  9. — EXPANSION  CUSHION.  An  expansion  cushion 
must  be  provided  for,  one  inch  in  thickness  next  to  the  curb, 
filled  two-thirds  of  its  depth  with  pitch,  the  top  one-third  being 
filled  with  sand. 

EXTRA  MENTION 

This  pitch  joint  next  to  and  along  the  curb  answers  two 
purposes,  it  takes  up  the  expansion  of  the  brick  and  prevents  a 
possible  cracking  of  the  pavement  through  and  along  the  centre 
of  the  street,  which  sometimes  occurs  if  the  ends  of  the  courses 
of  the  brick  are  abutted  directly  against  the  curb,  which  acts 
as  a  skewback  or  haunch  to  the  arc  of  the  pavement,  which  is 
often  strong  enough  (especially  if  the  sidewalk  is  up  to  and 
against  the  inside  of  the  curb)  to  resist  the  force  of  expansion  in 
that  direction,  and  it  will  find  relief  in  raising  the  pavement 
and  the  cracking  mentioned  above  may  occur.  And  again,  in 
taking  up  the  expansion  the  brick  are  kept  in  contact  with  the 


218  HIGHWAY  ENGINEERING 

sand  cushion  below,  thereby  preventing  the  rumbling  noise  so 
often  heard,  and  occasioned  wholly  through  lack  of  contact. 

The  inch  of  sand  on  the  top  of  the  pitch  joint  has  a  tendency 
to  prevent  the  pitch  from  flowing,  which  it  is  likely  to  do  in 
very  hot  weather.  It  is  essential  that  the  board  occupying  the 
place  to  be  filled  with  pitch  remain  in  place  until  after  the 
street  is  in  all  other  respects  finished,  but  always  withdrawn 
and  the  pitch  applied  within  thirty-six  hours  after  the  application 
of  the  cement  filler. 

SECTION  10. — THE  FILLER.  The  filler  shall  be  composed  of  one 
part  each  of  clean  sand  and  Portland  cement.  The  sand  should 
be  dry.  The  mixture,  not  exceeding  one-third  bushel  of  the  sand 
together  with  a  like  amount  of  cement,  shall  be  placed  in  the  box 
and  mixed  dry,  until  the  mass  assumes  an  even  and  unbroken 
shade.  Then  water  shall  be  added,  forming  a  liquid  mixture 
of  the  consistency  of  thin  cream. 

From  the  time  the  water  is  applied  until  the  last  drop  is 
removed  and  floated  into  the  joints  of  the  brick  pavement,  the 
same  must  be  kept  in  constant  motion. 

The  mixture  shall  be  removed  from  the  box  to  the  street 
surface  with  a  scoop  shovel,  all  the  while  being  stirred  in  the 
box  as  the  same  is  being  thus  emptied.  The  box  for  this  pur- 
pose shall  be  3}  to  4  ft.  long,  27  to  30  ins.  wide,  and  14  ins.  deep, 
resting  on  legs  of  different  lengths,  so  that  the  mixtures  will 
readily  flow  to  the  lower  corner  of  the  box,  which  should  be  from 
8  to  10  ins.  above  the  pavement.  This  mixture,  from  the  mo- 
ment it  touches  the  brick,  shall  be  thoroughly  swept  into  the 
joints. 

Two  such  boxes  shall  be  provided  in  case  the  street  is  twenty 
feet  or  less  in  width ;  exceeding  twenty  feet  in  width,  three  boxes 
should  be  used. 

The  work  of  filling  should  thus  be  carried  forward  in  line 
until  an  advance  of  fifteen  to  twenty  yards  has  been  made,  when 
the  same  force  and  appliances  shall  be  turned  back  and  cover  the 


BRICK   PAVEMENTS  219 

same  space  in  like  manner,  except  to  make  the  proportions  two- 
thirds  Portland  cement  and  one-third  sand. 

To  avoid  the  possibility  of  the  thickening  at  any  point, 
there  should  be  a  man  with  a  sprinkling  can,  the  head  per- 
forated with  small  holes,  sprinkling  gently  the  surface  ahead  of 
the  sweepers. 

Within  one-half  to  three-quarters  of  an  hour  after  this  last 
coat  is  applied  and  the  grout  between  the  joints  has  fully  sub- 
sided and  the  initial  set  is  taking  place,  the  whole  surface  must 
be  slightly  sprinkled  and  all  surplus  mixture  left  on  the  tops 
of  the  bricks  swept  into  the  joints,  bringing  them  up  flush 
and  full. 

After  the  joints  are  thus  filled  flush  with  the  top  of  the 
bricks  and  sufficient  time  for  evaporation  has  taken  place,  so 
that  the  coating  of  sand  will  not  absorb  any  moisture  from 
the  cement  mixture,  one-half  inch  of  sand  shall  be  spread  over 
the  whole  surface,  and  in  case  the  work  is  subjected  to  a  hot 
summer  sun,  an  occasional  sprinkling,  sufficient  to  dampen  the 
sand,  should  be  followed  for  two  or  three  days. 

EXTRA  MENTION 

Dry,  sharp  sand  for  this  mixture  is  necessary  without  ques- 
tion or  comment. 

The  first  application  should  be  thin  in  order  that  it  may 
flow  to  the  depth  of  the  joints  of  the  bricks,  thereby  insuring  a 
substantial  bond,  and  should  be  kept  in  constant  motion  while 
being  applied;  otherwise  the  sand  will  settle  and  you  will  have 
water  and  cement  instead  of  water,  sand,  and  cement.  The  water 
and  cement  wouldn't  be  objectionable,  but  the  sand  by  itself  is 
wholly  so. 

It  must  also  be  mixed  in  small  quantities,  as  it  is  next  to 
impossible  to  keep  the  sand  in  suspension  when  more  than  a 
common  water  pail  of  each,  sand  and  cement,  is  used,  and  un- 
less it  is  deposited  upon  the  pavement  with  the  sand  hi  combi- 


220 


HIGHWAY  ENGINEERING 


nation  with  the  solution  you  will  get  the  cement  and  water  in 
the  lower  portion  of  the  joints  between  the  bricks  and  the  sand 
without  the  cement  in  the  upper  portion.  If  you  could  get  the 
sand  in  the  lower,  and  the  cement  in  the  upper  portion  of  said 
joints,  you  would  have  a  good  grouted  street.  Some  one,  some 
day,  may  perfect  a  mechanical  device  for  doing  this  satisfac- 
torily, but  at  this  time  no  such  method  is  known.  The  rocking 
trough  has  been  tried  for  the  mixing  and  discharging,  but  in- 
variably the  cement  will  flow  out  first,  then  follows  the  sand  to 
fill  the  upper  parts  of  the  joints;  therefore,  the  safest  way  is  to 
use  the  scoop  shovel  as  the  specifications  direct. 

Ten  days  is  the  minimum  time  for  keeping  the  street  block- 
aded and  free  from  traffic.  Thirty  days  would  be  better, 
and  longer  if  it  were  possible.  In  testing-laboratories  the  usual 


AFTER  ROLLING 


FIG.  60. 


time  for  allowing  cements  (neat  cements  at  that)  to  stand  before 
applying  the  tests,  is  twenty-seven  days.  Therefore,  when  you 
open  a  grouted  street  to  traffic  in  ten  days  you  are  demanding 
and  expecting  more  from  the  cement  than  any  testing-laboratory 
would,  so  the  streets  should  remain  closed  as  long  as  a  suffer- 
ing public  will  permit. 

It  is  urgently  insisted  that  in  no  case  shall  the  proportion 
of  cement  be  lessened. 

Grouting  thus  finished  must  remain  absolutely  free  from 
disturbance  or  traffic  of  any  kind  for  a  period  of  ten  days 


BRICK  PAVEMENTS  221 

at  least.  The  specifications,  closely  and  skilfully  followed, 
will  give  you  the  three  important  factors  of  a  desirable  city 
thoroughfare— DURABILITY,  COMFORT  OF  TRAVEL, 
PERFECT  SATISFACTION. 

The  foregoing  are  some  of  the  many  reasons  why  the  above 
instructions  for  brick  street  building  should  be  embodied  in  all 
specifications  by  the  authorities. 


CHAPTER  IX 
ASPHALT    PAVEMENTS 

"  ASPHALT  is  a  term  which  may  be  used  industrially  or 
specifically;  industrially,  to  cover  all  solid  native  bitumen  (i.e., 
all  solid  native,  natural  hydrocarbons)  used  in  the  paving 
industry;  and  specifically,  to  include  such  as  melt  on  the  applica- 
tion of  heat  at  about  the  temperature  of  boiling  water,  are  equally 
soluble  in  carbon  bisulphide  and  carbon  tetrachloride,  and  to  a 
very  large  extent  in  eighty-eight  degrees  naphtha,  consisting 
to  a  very  considerable  degree  of  saturated  hydrocarbons  yielding 
about  fifteen  per  cent  of  fixed  carbon  and  containing  a  high 
percentage  of  sulphur." 

An  asphalt  pavement  is  one  in  which  the  principal  and  dis- 
tinguishing, though  not  the  largest,  constituent  of  the  wearing 
surface  is  asphalt. 

Asphalt  may  be  distinguished  by  the  following  characteris- 
tics: 

Sp.  Gr.     =0.96  to  1.68. 

Color        =dark  brown  to  glittering  black. 

Hardness  =  liquid  to  3J  Dana  Scale. 

Streak      =  brown  to  brownish  black. 

Fracture  =dull  to  conchoidal. 

Odor        =  bituminous. 

Insoluble  in  H20,  soluble  in  carbon  bisulphide,  alcohol, 
turpentine,  ether,  naphtha,  and  petroleum.  Before  the 
blow  pipe  it  melts  quickly,  evaporates,  and  burns,  leaving 
no  ash. 

Chemically,  when  pure,  asphalt  contains: 

222 


ASPHALT  PAVEMENTS  223 

C=80   to  88  per  cent 


(J=8U  to  88  per  cent 
O=  0.5  to  10  per  cent 
H=  9  to  11  per  cent 
N=  0  to  1  per  cent 


Asphalt  is  found  in  a  liquid,  semi-liquid,  or  solid  state,  or  else 
impregnating  the  sandstones  or  limestones.  In  the  former 
state  it  is  always  mixed  with  water  together  with  some  organic 
and  inorganic  impurities,  and  for  this  reason  it  becomes  necessary 
for  it  to  undergo  a  refining  process  during  the  course  of  which  the 
water  and  volatile  oils  are  driven  off  and  the  organic  impurities 
gotten  rid  of.  It  does  not  matter  so  much  about  the  inorganic 
impurities  or  mineral  matter  contained  within  the  asphalt, 
since  under  all  conditions  it  is  necessary  to  add  some  such  con- 
stituent to  the  latter  to  form  the  wearing  surface. 

The  material  mostly  used  in  the  United  States  for  paving 
purposes  comes  from  the  island  of  Trinidad  off  the  north  coast 
of  Venezuela,  South  America,  or  from  the  province  of  Bermudez 
in  Venezuela,  the  former  being  known  as  Trinidad,  and  the  latter 
as  Bermudez  asphalt. 

In  the  crude  state  they  contain  the  folio  whig  constituents: 

Trinidad         Bermudez 
Per  Cent  Per  Cent 

Water  and  gas 29 

Organic  matter  not  bitumen 7  1 . 5  to    9 

Mineral  matter 25  1 . 5  to    3 

Bitumen 39  89.2  to  97 

It  will  be  seen  from  this  that  the  Bermudez  asphalt  is  very 
much  purer  than  the  Trinidad,  consisting  of  nearly  pure  bitumen. 
The  bitumen  itself  analyzes  a  follows: 

T.  B. 

C 82.33  82.88 

H 1 0 . 69  10 . 79 

S 6.16  5.87 

N..                                              0.81  .75 


99.99       100.29 


224  HIGHWAY   ENGINEERING 

The  refined  asphalts  have  the  following: 

PHYSICAL  CHARACTERISTICS 

T.  B. 

Sp.  Gr.— at  78°  F.,  original  substance  dry 1 . 40  1 . 05 

Color  of  powder blue  black  black 

Lustre dull  bright 

Structure homogeneous  uniform 

Fracture semi-conchoidal  uniform 

Hardness,  original  substance 2                   soft 

Odor asphaltic              soft 

Softness 180°  F.  160°  F. 

Flows 190°  F.  170°  F 

Penetration  at  78°  F 7°                    26° 

CHEMICAL  CHARACTERISTICS 

Dry  Substance. 

Loss  325°  F.,  7  hrs 1 . 1  per  cent  4.4  per  cent 

Character  of  residue smooth  4 . 4  per  cent 

Loss  400°  F.,  7  hrs.  (fresh  sample) 4  per  cent  9 . 5  per  cent 

Character  of  residue blistered             shrunken 

Bitumen  soluble  in  CSa,  air  temp 56.4  per  cent  96. 0  per  cent 

Organic  matter  insoluble 6.7  per  cent  2 . 0  per  cent 

Inorganic  or  mineral  matter 36 . 9  per  cent  2 . 0  per  cent 

100.0  per  cent     100.0  per  cent 

Asphalts  from  Maracaibo,  Cuba,  Mexico,  and  California 
differ  somewhat  from  those  mentioned  above;  but  they  are  found 
in  such  limited  quantities,  however,  that  they  have  little  com- 
mercial value.  The  evaporation  of  a  petroleum  oil  with  an 
asphalt  base  will  also  yield  a  residue  like  the  native  asphalts,  the 
supply  coming  mostly  from  California  and  Texas,  where  such  oils 
are  found ;  but  the  process  of  manufacture  requires  such  care  and 
skill  that  most  of  the  product,  up  to  the  present,  is  hardly  satis- 
factory. The  distinguishing  characteristic  between  this  and  the 
native  asphalts  is  that  the  latter  contain  mineral  matter,  while 
the  former  do  not. 

In  Kentucky,  Tennessee,  Texas,  Utah,  and  California  impreg- 


ASPHALT   PAVEMENTS  225 

nated  sand  and  limestones  are  found  in  considerable  quantities, 
but  they  are  hardly  ever  so  satisfactory  for  paving  purposes  as 
the  artificial  material.  The  natural  limestones  make  the  harder 
but  more  slippery  pavement,  while  the  sandstones  frequently 
have  too  little  bitumen  in  them  to  hold  the  sand  grains  together. 

Asphalt  pavements  may  be  classified  as  follows :  Natural,  as 
opposed  to  artificial-asphalt  pavements;  and  sheet,  as  opposed  to 
block  pavements. 

Natural-asphalt  pavements  may  be  either  in  the  sheet  or 
block  form,  consisting  of  a  wearing  surface  of  the  naturally 
impregnated  stone.  In  this  country  the  natural  pavement  is 
used  to  some  extent,  and  where  so  used  preference  seems  to  be 
given  generally  to  the  sandstones  rather  than  the  limestones,  as 
they  wear  more  evenly,  do  not  polish,  and  thus  afford  greater 
advantages  to  traction  and  as  regards  the  foothold.  On  the 
other  hand,  the  limestones  are  very  much  more  durable.  Abroad 
the  asphaltic  limestones  are  much  more  abundant  than  the  sand- 
stones, and  consequently  much  more  generally  used. 

Both  will  contain  about  the  same  amount  of  bitumen,  how- 
ever; that  is,  the  limestones  are  made  up  of  88  per  cent  carbonate 
of  lime  with  12  per  cent  of  bitumen,  while  the  sandstones  contain 
from  7  to  13  per  cent  of  the  latter  constituent. 

Where  natural  sand  rock  impregnated  with  asphalt  is  used, 
the  pavement  is  constructed  as  follows.  First,  the  sand  rock 
itself  is  ground,  and  it  is  then  heated  to  a  temperature  of  300° 
F.  and  spread  on  a  clean,  concrete  base,  rolled  and  rammed  to  a 
thickness  of  two  inches.  No  flux  is  used  with  the  sand  rock,  as 
the  bitumen  present  is  found  to  be  quite  cementitious  enough 
and  no  binder  course  is  found  necessary.  Sometimes  this  sand 
is  mixed  with  limestone  rock  in  the  proportion  of  1  to  1  or  2  to  1, 
depending  upon  the  amount  of  bitumen  present. 

Such  natural  pavements  have  been  found  eminently  satis- 
factory in  Buffalo,  where  they  cost  annually  but  J  to  i  in  repairs 
of  what  the  artificial  pavements  do. 
15 


226  HIGHWAY  ENGINEERING 

Artificial-asphalt  pavement  is  a  name  applied  to  one  in  which 
the  wearing  coat  consists  of  a  mixture  of  sand,  limestone  or  silica 
dust,  and  asphaltic  cement,  which  constituents  are  artificially 
commingled.  The  sand  is  for  the  purpose  of  taking  the  wear  the 
same  as  the  naturally  impregnated  sandstones  or  limestones, 
while  the  asphalt  performs  the  function  of  cementing  these  parti- 
cles together  in  exactly  the  same  way  as  is  done  naturally  in  the 
sandstones  and  limestones.  The  function  of  the  limestone  or 
silica  dust  is  to  fill  the  voids  between  the  sand  grains  and  thus 
save  the  expensive  material. 

ARTIFICIAL  PAVEMENTS  are  built  either  in  the  sheet  or  block 
form,  and  in  America  at  least  are  the  much  more  satisfactory 
pavement. 

The  principal  advantages  of  an  asphalt  pavement,  whether 
sheet  or  block,  natural  or  artificial,  are  that, 

(1)  It  reduces  tractive  force. 

(2)  It  is  impervious. 

(3)  It  is  easily  cleaned. 

(4)  It  is  durable. 

(5)  It  is  noiseless. 

(6)  It  produces  no  dust  or  mud, 
while  its  disadvantages  are, 

(1)  It  is  slippery  under  certain  weather  conditions. 

(2)  It  is  affected  to  some  degree  by  heat  or  cold,  the  former 
softening  it  and  causing  it  to  wave,  while  the  latter  will  produce 
cracks. 

(3)  It  is  not  especially  good  on  heavy  grades. 

(4)  It  is  expensive. 

(5)  Excessive  moisture  disintegrates  it. 

(6)  It  must  have  an  absolutely  unyielding  foundation,  as 
otherwise  it  is  easily  broken  down. 

An  asphalt  pavement  consists  of  three  essentially  different 
parts:  1st,  the  foundation;  2d,  the  binder  course;  and  3d,  the 
wearing  surface. 


ASPHALT   PAVEMENTS  227 


THE   FOUNDATION 

The  foundation  is  a  particularly  important  factor  in  the 
case  of  asphalt  pavements,  as  asphalt  in  itself  possesses  no 
resistance  to  crushing  and  simply  performs  the  function  of  tak- 
ing up  the  wear.  If  the  foundation  hence  is  not  absolutely 
unyielding,  the  asphalt  will  have  no  power  to  counteract  this 
lack  of  strength,  and  the  pavement  will  soon  be  filled  with 
depressions  that  are  quickly  converted  into  holes  by  the  action 
of  traffic  and  the  disintegrating  effects  of  moisture  collected 
therein. 

At  present  the  most  popular  and  most  satisfactory  foundation 
for  asphalt  pavements  is  a  hydraulic  concrete.  This  is  made  of 
natural  or  artificial  cement,  in  the  proportions  of  1  cement  to 
2  sand  (4-6  broken  stone)  or  1  cement  to  3  sand  (5-7  broken 
stone),  and  varies  in  depth,  depending  upon  the  nature  of  the 
subsoil,  amount  of  traffic,  etc.,  etc.,  from  4  ins.  to  6  ins. 

With  a  concrete  base  it  has  been  found  that  the  surfacing  is 
apt  to  strip  off  rather  easily,  but  while  this  is  an  advantage  as 
regards  the  matter  of  repairs,  it  is  a  disadvantage  in  the  fact  that 
the  surface  is  not  so  firmly  held  to  the  foundation,  and  hi  conse- 
quence the  former  is  apt  to  roll  and  crack  under  extremes  of 
temperature. 

Concrete  is,  under  nearly  all  circumstances,  the  best  founda- 
tion, for  it  forms  an  impervious  covering  for  the  subsoil  and 
possesses  great  strength.  When,  the  street  has  never  before  been 
paved,  concrete  is  always  selected  for  these  reasons. 

It  has  frequently  occurred,  however,  that  "  much  of  the  sheet 
asphalt  in  the  great  cities  has  been  put  directly  upon  old  pave- 
ments of  cobbles  or  of  stone  blocks,  of  which  the  depressions  may 
be  filled  with  hot  crushed  stone  sprinkled  with  hot  asphaltic 
cement,  or  which  may  be  merely  reset  at  points  of  subsidence  to 
restore  the  regular  form,  but  which  are  usually  reset  at  three 
inches  lower  grade  and  with  the  proper  crown  hi  order  to  make 


228  HIGHWAY   ENGINEERING 

room  for  the '  binder '  and '  wearing  surface '  of  asphalt  without  hav- 
ing to  raise  the  manholes,  car  tracks,  and  curbs.  The  joints  be- 
tween the  stones  of  the  old  pavements  should  be  three-quarters 
of  an  inch  wide  and  should  be  brushed  and  cleared  for  at  least  an 
inch  in  depth  to  afford  a  firm  hold  for  the  '  binder.'  In  some 
instances,  stone  blocks  for  a  base  have  been  relaid  flat  to  give  a 
lower  grade,  but  this  is  not  good  practice  and  has  given  poor 
results  unless  there  is  a  concrete  base  beneath  the  old  blocks." 

"  Brick  pavement  and  macadam  have  been  successfully  used 
as  a  foundation  for  asphalt,  but  it  is  found  difficult  to  restore  the 
pavement  to  its  original  good  condition  when  cuts  have  to  be 
made  for  pipes  of  any  kind." 

Where  concrete  is  employed,  care  should  be  taken  to  see  that 
the  material  has  thoroughly  set  before  the  asphalt  is  applied, 
and  before  the  binder  is  put  on  all  moisture  should  be  removed 
from  the  surface  by  a  sponge  or  application  of  heat,  as  its  presence 
prevents  a  good  bond  between  binder  and  foundation. 

THE   BINDER 

The  binder  is  the  name  given  to  the  mixture  of  stone  and 
asphalt  cement  which  is  placed  next  the  foundation,  and  upon 
which  the  wearing  surface  proper  is  laid,  and  whose  function  it 
is  to  bind  the  two  together. 

The  stone  used  is  any  hard  tough  rock  which  has  been  crushed 
to  a  size  of  one  and  one-quarter  inches  or  less,  and  usually  con- 
tains some  of  the  coarser  screenings  of  the  sand.  Ninety-five  per 
cent  by  weight  of  stone  and  five  per  cent  of  asphalt  cement  are 
the  proportions  used,  though  this  amount  of  cement  will  vary  de- 
pending upon  voids.  The  mixture  of  cement  and  stone  should 
be  thorough,  and  so  complete  that  every  fragment  is  completely 
covered  with  the  cement. 

The  binder  is  brought  hot  to  the  place  from  the  mechanical 
mixer  and  spread,  by  means  of  rakes,  to  a  depth  of  about  two 
inches  over  the  concrete  foundation,  and  then  rolled  by  a  steam 


ASPHALT   PAVEMENTS  229 

roller  until  the  thickness  has  been  reduced  to  one  and  one-half 
inches. 

The  surface  of  the  binder  course  should  be  made  parallel  to 
the  finished  coating,  and  must  be  so  firm  that  it  is  not  displaced 
by  the  passage  of  teams. 

WEARING   SURFACE 

The  topmost  layer  of  an  asphalt  pavement,  that  is,  the  wear- 
ing coat,  is  composed  of  sand,  limestone  or  silica  dust,  and  as- 

phaltic  cement. 

80  per  cent  sand. 

10  per  cent  asphaltic  cement. 

10  per  cent  stone  dust. 

THE  SAND,  constituting  about  80  per  cent  of  the  wearing  sur- 
face, should  be  hard,  clean,  sharp,  and  have  few  voids.  This  is 
the  material  that  really  takes  the  wear  while  the  asphalt  simply 
binds  the  grains  together.  The  greater  resistance  to  wear  and 
crushing  hence  possessed  by  the  sand  the  longer  the  life  of  the 
pavement.  If  the  grams  are  sharp  and  angular,  there  will  be  a 
good  mechanical  bond  similar  to  that  existing  in  broken  stone, 
and  if  the  voids  are  few  there  will  be  less  need  of  the  other 
materials,  i.e.,  the  stone  dust  and  asphalt,  to  fill  these  voids; 
and  it  will  hence  require  less  of  the  expensive  material  asphalt  to 
bind  the  whole  together,  thus  reducing  the  cost  of  the  pavement. 
The  size  of  the  grains  should  vary  so  as  to  diminish  the  amount  of 
voids  as  much  as  possible. 

THE  STONE  DUST  may  be  either  limestone  or  silica,  and  its 
function  is  more  completely  to  fill  the  voids  between  the  grains  of 
sand.  The  proportion  of  stone  dust  to  sand  depends  upon  the 
percentage  of  voids  in  the  sand,  and  the  relation  must  be  deter- 
mined by  trial,  as  the  best  ratio  is  when  the  combined  sand  and 
stone  dust  yield  the  smallest  percentage  of  interstices. 

To  determine  this  ratio  varying  amounts  of  stone  dust  are 
mixed  in  a  pail  with  a  constant  quantity  of  sand  and  the  resulting 
voids  ascertained  by  pouring  in  enough  water  to  flush  the  surface 


230  HIGHWAY   ENGINEERING 

of  the  mixture.  That  combination  requiring  the  least  amount 
of  water  is  the  most  satisfactory  as  then  less  asphalt  is  needed. 
Necessarily  this  will  vary  with  the  nature  of  the  sand,  but  usually 
from  5  to  15  per  cent  of  dust  is  needed. 

This  stone  dust  should  be  so  fine  that  all  of  it  will  pass  a  30 
mesh,  per  linear  inch,  sieve,  and  75  per  cent  pass  a  100  mesh  sieve. 

In  regard  to  the  use  of  carbonate  of  lime  or  silica  dust  it  would 
seem  that  the  latter  is  more  satisfactory,  as  it  is  the  less  slippery 
and  is  not  soluble  in  rain  water  containing  C02  gas. 

THE   ASPHALT 

The  asphalt  or  asphaltic  cement  consists  of  refined  asphalt 
mixed  with  a  flux  or  softening  agent.  The  refined  asphalt  is  the 
crude  asphalt  with  water  and  volatile  oils  driven  off,  and  to  this 
is  added  the  flux  which  varies  in  character,  but  has  the  property 
of  reducing  the  brittleness  or  hardness  of  the  refined  asphalt  to 
form  the  asphaltic  cement  which  possesses  the  binding  properties 
in  the  surface  cost.  The  fluxes  should  possess  the  following 
properties : 

"  (1)  Contain  a  material  volatile  under  300°  F.  as  otherwise 
the  volatile  matter  will  be  given  off  while  the  paving  cement 
is  being  heated  preparatory  to  its  being  mixed  with  the  sand 
of  the  wearing  coat,  and  consequently  the  asphalt  will  lose  its 
cementing  power. 

"  (2)  The  flux  should  be  as  fluid  as  possible  in  order  that  the 
greatest  softening  effect  may  be  produced  by  the  least  quantity, 
as  ordinarily  the  fluxing  agent  is  comparatively  expensive. 

"  (3)  The  softening  agent  should  be  chemically  stable,  and 
not  lose  its  fluidity  by  molecular  change. 

"  (4)  The  fluxing  agent  should  dissolve  the  asphalt,  and  not 
simply  form  a  mechanical  mixture  with  it.  The  asphalt  consists 
of  asphaltine  and  petroline;  the  former  being  entirely  devoid 
of  cementing  power,  and  the  latter  highly  cementitious;  and 
hence  the  fluxing  agent  should  dissolve  the  asphaltine." 


ASPHALT  PAVEMENTS  231 

The  fluxes  themselves  are  petroleum  residuum,  maltha, 
which  is  a  liquid  bitumen,  and  the  asphaltic  oils;  and  the 
amount  to  be  used  will  vary  both  with  the  flux  and  the  nature 
of  the  refined  asphalt.  It  is  a  question  which  is  best. 

The  thickness  of  the  wearing  surface  is  about  2J  ins.,  2  ins. 
after  rolling,  for  heavy  traffic,  and  1J  ins.,  compressed,  for  light 
traffic. 

The  wearing  coat  is  brought  to  the  place  hot,  at  a  tempera- 
ture of  about  280°  F.  and  laid  and  spread  with  hot  rakes  to  a 
depth  of  2J  ins.  and  rolled  till  only  1 J  ins.  or  to  a  depth  of  3J  ins. 
and  rolled  till  only  2  ins.  This  latter  is  the  better  thickness, 
particularly  for  heavy  traffic. 

The  surface  of  wearing  coat  is  first  rolled  with  a  1,200  Ibs.  hand 
roller,  which  is  cold,  and  which  is  constantly  wiped  with  oily 
cotton  waste  to  prevent  the  adhesion  of  any  of  wearing  coat. 
Hydraulic  cement  is  then  swept  over  the  surface  to  give  a  gray 
color  to  it  and  prevent  adhesion,  when  a  5  ton  roller  is  used  for 
the  final  compression.  This  rolling  will  require  1  hour  to  every 
60X30  =  1,800  sq.ft. 

GRADE   AND   CROWN 

"  The  actual  steepest  grades  existing  in  various  cities  are 
shown  in  the  accompanying  table,  in  order  that  those  having 
doubts  in  any  extreme  case  may  examine  some  of  these  grades 
and  observe  the  results. 

ACTUAL  GRADES  OF  SHEET  ASPHALT 

Ft.  per  Ft.  per 

City  and  State.  100  ft.          City  and  State  100  ft. 

Buffalo,  N.  Y 5.1  Pittsburg,  Penn 17 

Erie,  Penn. 5  Salt  Lake  City,  Utah 5 

Grand  Rapids,  Mich 7  San  Francisco,  Cal 16 

Hartford,  Conn 5  St.  Joseph,  Mo 8 

Marion,  0 5.75  Scranton,  Penn 13 

New  York,  N.  Y 5  Syracuse,  N.  Y 7 

Omaha,  Neb 8  Toledo,  0 5 

Peoria,  111 7.2  Troy,  N.  Y 75 


232  HIGHWAY  ENGINEERING 

"  The  crown  used  in  various  cities  on  level  streets  is  shown  in 
the  same  way ;  it  being  borne  in  mind  that  the  least  crown  which 
will  shed  water  makes  the  best  road  for  those  who  use  it." 

ACTUAL  "CROWN"  OF  SHEET  ASPHALT 

Inches  per  30  ft.  Inches  per  30  ft. 

City  and  State.  width  bet.  curb.          City  and  State  width  bet.  curb. 

Albany,  N.  Y 5  Jackson,  Mich 4£ 

Atlanta,  Ga 5  Joliet,  111 5 

Binghamton,  N.  Y 5  Mansfield,  0 5£ 

Buffalo,  N.  Y 5  Meriden,  Conn 4 

Charleston,  S.  C 4  Milwaukee,  Wis 11 

Columbus,  0 6  Muncie,  Ind 12 

Dayton,  0 4£  New  Orleans,  La 5 

Detroit,  Mich 3|  Peoria,  111 6 

Elmira,  N.  Y 4$  Sandusky,  0 6 

Erie,  Perm 6  Scranton,  Penn 5 

Fort  Wayne,  Mich 4  Springfield,  Mass 3£ 

Grand  Rapids,  Mich 6  St.  Paul,  Minn 5£ 

Harrisburg,  Penn 5  Terre  Haute,  Ind 7 

Hartford,  Conn 4£  Toronto,  Ont 7 

Houston,  Tex 6  Troy,  N.  Y 5£ 

Where  street-railway  tracks  exist  on  an  asphalted  street,  it  is 
usually  customary  to  place  some  other  material  than  asphalt  next 
the  rail  to  permit  of  wagons  turning  into  or  out  from  the  track 
without  damaging  the  asphalt  and  causing  a  shoulder  as  they 
inevitably  would  do  were  the  asphalt  used.  In  New  York 
City  granite  blocks  are  placed  between  the  rails  and  a  header  and 
stretch  next  the  rails  on  the  outer  side.  Stone  or  brick  is  often 
used. 

Where,  as  in  some  of  the  larger  cities,  such  as  Buffalo,  a 
heavy  rail  of  90  Ibs.  with  a  large  web  9  to  10  ins.  is  used,  with 
welded  joints  and  a  concrete  base,  it  is  feasible  to  lay  the  asphalt 
close  up  to  the  rail. 

BLOCK  ASPHALT 

This  is  formed  of  about  13  per  cent  asphaltic  cement,  10  per 
cent  limestone  dust,  and  77  per  cent  crushed  gneiss,trap,  basalt,  or 
other  hard  rock.  Basalt  is  usually  preferable. 

The  material  is  heated  to  300  °  F.  in  a  rotary  mixer  until  all 


ASPHALT   PAVEMENTS  233 

the  particles  have  become  perfectly  coated  with  the  limestone 
dust  and  cement  and  then  moulded  into  blocks  12  ins.  X  (4  to 
5  ins.)X(3  to  4  ins.)  by  a  pressure  of  2J  tons  per  sq.  in.;  and 
finally  cooled  in  water. 

The  advantages  of  this  sort  of  pavement  are : 

(1)  It  may  be  laid  in  cold  weather. 

(2)  No  skilled  labor  required. 

(3)  Requires  no  plant,  hence  good  for  small  towns. 

But  it  is  not  so  good  as  the  sheet  form.  Has  cracks,  hence 
not  so  impervious,  not  so  clean,  not  so  noiseless.  The  best  base  is 
concrete,  but  it  is  sometimes  laid  on  gravel  covered  with  sand. 

Below  are  given  the  complete  specifications  for  both  sheet 
and  block-asphalt  pavements. 

SPECIFICATIONS 

For  Regulating,  Grading,  and  Paving  or  Repaving  with  Asphalt 
Pavement  on  a  Concrete  Foundation  the  Roadway  of 

From  

To 

together  with  all  work  incidental  thereto. 

1.  EXTENT  OF  WORK.     The  work  shall  consist  of  regulating 
and  grading  the  entire  street  (or  if  the  street  is  already  paved,  of 
removing  or  readjusting  the  old  pavement),  setting  and  resetting 
curb,  laying  sidewalks  where  required,  and  laying  asphalt  pave- 
ment and  all  work  incidental  thereto,  all  in  accordance  with  the 
plans  and  specifications  on  file  hi  the  office  of  the  Bureau  of 
Highways. 

2.  OBSTRUCTIONS.     The  contractor  shall  remove  at  his  own 
expense,  when  directed  by  the  engineer,  any  encumbrances  or 
obstructions  on  the  line  of  work,  located  or  placed  there  prior  to 
or  after  its  commencement. 

3.  CATCH-BASINS,  MANHOLE  HEADS,  ETC.    Such  catch-basins, 


234  HIGHWAY   ENGINEERING 

manhole  frames  and  heads  for  sewers,  water  pipes  or  other  con- 
duits belonging  to  the  City  on  the  line  of  the  work,  as  may  be 
designated,  shall  be  reset  to  the  new  grades  and  lines  by  the  con- 
tractor without  extra  charge  therefor,  arid  they  shall  be  brought 
to  such  grades  with  brick  masonry  of  the  same  thickness  as  that 
originally  used,  laid  in  hydraulic  cement  mortar. 

4.  NOISELESS    MANHOLE    COVERS.     Asphalt-filled    noiseless 
covers,  complete,  for  water  and  sewer  manholes  of  the  design 
approved  by  the  engineer,  shall  be  furnished  and  set  wherever 
directed  by  the  engineer.     They  shall  be  made  according  to 
general  details  to  be  furnished  to  the  contractor  and  of  such  size 
as  will  fit  the  present  manhole  heads.     The  old  covers  to  remain 
the  property  of  the  City. 

5.  REMOVAL  AND  OWNERSHIP  OF  OLD  MATERIALS.     All  old 
material  which  will  not  be  used  in  the  work,  excepting  bridge- 
stone  and  specification  paving  stone,  shall  become  the  property 
of  the  contractor  and  be  removed  by  him;  the  remainder,  as 
specified  above,  shall  be  delivered  when  required,  and  piled  in 
such  corporation  yard  or  elsewhere  as  the  engineer  may  deter- 
mine, and  all  at  the  expense  of  the  contractor. 

6.  PREPARATION  OF  FOUNDATION.     When  the  old  material 
has  been  removed,  that  to  be  used  again  shall  be  compactly  piled 
on  the  side  and  the  roadway  graded  to  the  required  shape  and 
depth  below  the  proposed  finished  pavement.     All  unsuitable 
material  shall  be  removed  and  replaced  with  that  which  is  satis- 
factory.    Whenever  deemed  necessary  by  the  engineer,  the  sub- 
grade  shall  be  rolled  by  a  suitable  steam  roller. 

7.  RELAYING  STONE  PAVEMENT.  When  the  present  pavement 
is  specified  as  a  foundation,  any  and  all  portions  thereof  unfitted 
for  the  purpose  by  reason  of  grade  or  otherwise  shall  be  taken 
up  and  relaid  as  may  be  directed,  and  for  such  purpose  the 
materials  necessary  to  be  removed  shall  be  piled  or  disposed  of 
as  heretofore  specified. 

...'8.  On  the  roadbed  graded  and  prepared  as  hereinbefore  set 


ASPHALT   PAVEMENTS  235 

forth,  the  stones  shall  be  relaid  at  right  angles  to  the  line  of  the 
street.  They  shall  be  well  bedded  on  gritty  earth  or  other 
material  approved  by  the  engineer,  with  surface  joints  not  ex- 
ceeding one  (1)  inch,  the  joints  to  be  brushed  full  of  the  same 
material  and  the  stones  rammed  to  a  solid,  unyielding  foundation, 
with  their  top  surface  parallel  to  and  three  (3)  inches  below  the 
surface  of  the  pavement  to  be  laid.  Such  additional  stones  as 
may  be  required  shall  be  supplied  by  the  contractor  without 
charge  therefor. 

9.  INSPECTION  AND  PILING  OF  MATERIAL.     The  material  for 
construction  when  brought  upon  the  street  shall  be  neatly  piled 
so  as  to  present  as  little  obstruction  to  travel  as  possible.     No 
material  shall  be  used  without  having  been  first  inspected  and  ac- 
cepted by  the  engineer,  the  contractor  furnishing  all  labor  neces- 
sary for  inspection  without  any  charge.     Should  the  work  be 
suspended  for  any  cause  the  materials  shall  be  removed  from  the 
line  of  the  work  at  the  direction  of  the  engineer,  and  unless  so 
removed  by  the  contractor  upon  notice  from  the  said  engineer, 
they  will  be  removed  by  the  president,  and  the  expense  thereof 
charged  to  the  contractor. 

10.  CITY  MONUMENTS.     The  contractor  shall  not  excavate 
around  such  city  monuments  and  bench-marks  as  may  come 
within  the  limits  of,  or  be  disturbed  by  the  work  herein  contem- 
plated nearer  than  five  (5)  feet,  or  in  any  manner  disturb  the 
same,  but  shall  cease  work  at  such  locations  until  the  said  monu- 
ments or  marks  have  been  referenced  and  reset  or  otherwise  dis- 
posed of  by  the  chief  engineer  of  the  Bureau  of  Highways.     The 
necessary  labor  to  remove,  care  for,  and  reset  all  such  monuments 
and  bench-marks  shall  be  furnished  without  charge  therefor  by 
the  contractor. 

11.  EXCAVATION  AND  GRADING.     All  material  of   every  de- 
scription— earth,  rock,  subsoil,  vegetable  or  other  matter,  brick 
and  stone  masonry — overlying  the  subgrade  hereafter  described, 
shall  be  removed  and  the  roadway  and  sidewalks  freed  from  all 


236  HIGHWAY   ENGINEERING 

stones,  and  shaped  as  shown  on  plans.  Excavations,  of  whatever 
character,  shall  extend  fully  to  the  lines  specified  on  the  plans. 
The  cost  of  grubbing  up  and  removing  any  trees,  shrubbery, 
fences,  timber,  pipes,  rubbish,  or  filth  shall  be  included  in  the 
price  bid  for  excavation. 

12.  The  excavation  shall  be  carried  to  the  established  grade 
and  the  sidewalks  shall  slope  upward  from  the  curb  grades  to- 
ward the  house  lines,  all  in  accordance  with  the  dimensions 
shown  on  the  plan  of  the  work  and  as  the  same  are  designated  on 
the  ground  by  the  engineer.     Should  any  soft,  spongy,  vegetable, 
or  other  objectionable  matter  be  disclosed  by  the  excavation  thus 
made,  or  be  located  where  filling  is  to  be  done,  such  material  shall 
be  removed  and  replaced  with  coarse  sand,  gravel,  or  other  suit- 
able material,  which  shall  be  thoroughly  compacted,  as  herein- 
after directed,  at  the  price  herein  bid  for  earth  excavation. 

13.  FILLING  AND  EMBANKMENTS.     Embankments  shall  be 
brought  up  to  the  designated  grades,  and  the  top,  shaped  off  and 
compacted  as  defined  for  earth  excavation,  shall  extend  fully  to 
the  lines  and  be  maintained  at  the  designated  width  and  elevation 
until  the  expiration  of  the  period  of  maintenance.     Such  exca- 
vated material  as  may  be  fit  for  the  purpose  and  as  may  be  neces- 
sary shall  be  used  to  fill  in  those  parts  of  the  street  which  are 
below  the  aforesaid  grades,  or  which  have  become  so  by  the 
removal  of  rock  or  improper  material,  in  the  manner  hereafter 
provided,  and  the  price  paid  per  cubic  yard  of  excavation  is  to  in- 
clude the  cost  of  properly  placing  such  excavated  material  as 
filling  and  in  embankment,  and  the  removal  from  the  work  of 
such  as  is  not  so  utilized. 

14.  No  excavated  or  other  material  necessary  to  be  disposed 
of  shall  be  dumped  or  placed  within  the  limits  of  any  existing  or 
projected  public  street  or  road,  nor  shall  any  material  be  exca- 
vated and  removed  from  such  locations  without  the  written  per- 
mission of  the  engineer.     When  the  material  excavated,  fit  for 
filling,  is  insufficient  in  quantity  to  regulate  the  street,  such 


ASPHALT   PAVEMENTS  237 

additional  material  necessary  shall  be  furnished  and  placed  by 
the  contractor,  and  the  quantity  thereof  to  be  paid  for  as  "  filling 
to  be  furnished"  shall  be  the  difference  between  the  total  amount 
of  filling  done  or  excavation  made,  with  slopes  in  case  as  herein 
described,  and  to  the  grades  shown  on  the  cross-sections  of  the 
street. 

15.  The  total  amount  of  filling  done  will  be  determined  by 
calculation,  and  will  be  only  so  much  as  is  included  between  the 
elevation  of  said  surface  deposit,  as  recorded  by  the  engineer,  and 
the  grades  hereinbefore  set  forth  (where  such  filling  comes  up  to 
such  grades)  and  no  allowance  will  be  made  the  contractor  for  any 
shrinkage,  sinking,   or  settlement.    All  filling  shall  be  good, 
wholesome  earth,  free  from  all  frozen  materials,  garbage,  vege- 
tables, spongy  or  unsuitable  matter. 

16.  CURBSTONE.    Old  curbstone  which  can  be  redressed  to  a 
top  width  of  not  less  than  four  and  one-half  (4J)  inches  and  not 
less  than  sixteen  (16)  inches  deep  and  are  of  the  quality  hereafter 
specified,  shall  be  redressed,  rejointed,  and  reset   as   directed 
below. 

17.  QUALITY  OF.     New  curbstones  shall  be  free  from  seams 
and  other  imperfections  and  equal  in  quality  to  the  best  North- 
River  bluestone.     They  shall  be  (    )  niches  in  depth,  and 
from  three  and  one-half  (3J)  to  eight  (8)  feet  in  length  and  not 
less  than  five  inches  in  thickness,  except  as  noted  for  bottom  of 
curb. 

18.  How  DRESSED.     The  face  for  a  depth  of  nine  (9)  niches 
and  the  top  on  a  bevel  of  one-half  (J)  an  inch  in  its  width  of  five 
(5)  inches  shall  be  dressed  to  a  surface  which  shall  be  out  of  wind 
and  shall  have  no  depressions  measuring  more  than  one-quarter 
of  an  inch  from  a  line  or  straight  edge  of  the  same  length  as  the 
curbstone.     The  remainder  of  the  face  shall  be  free  from  pro- 
jections of  more  than  one-half  an  inch,  and  the  back  for  three  (3) 
inches  down  from  the  top  shall  have  no  projections  greater  than 
one-quarter  of  an  inch  measured  from  a  plane  at  right  angles  to 


238  HIGHWAY   ENGINEERING 

the  top.     The  bottom  of  the  curb  shall  be  rough-squared  with  a 
width  of  not  less  than  three  inches. 

19.  JOINTS  OF.     CURVED  CURB.     For  the  full  width  of  the 
stone  for  a  distance  down  of  four  (4)  inches  from  the  top,  and 
therebelow,  for  a  width  of  one  and  one-half  inches  back  from 
the  face  to  a  point  twelve  (12)  inches  below  the  top  of  the  curb, 
the  ends  shall  be  squarely  jointed  with  no  depression  greater  than 
three-eighths  of  an  inch,  measured  from  a  straight  edge.     Curved 
curb  corners  shall  be  cut  with  true  radial  joints  and  be  set  accu- 
rately to  such  a  radius  as  maybe  required  in  three  (3)  foot  lengths. 
It  shall  be  paid  for  as  straight  curb,  and  must  comply  in  all  re- 
spects with  the  above  requirements  therefor.     The  cost  of  ex- 
cavation necessary  for  curb-setting  shall  be  included  in  the  price 
paid  per  linear  foot  of  curb.     The  sample  of  the  curbstone  show- 
ing the  dressing  and  the  jointing  required  can  be  seen  at  the  office 
of  the  chief  engineer  of  the  Bureau  of  Highways. 

20.  WHEN  SET  IN  CONCRETE.     Where  the  pavement  is  to  be 
laid  on  concrete  the  curb  shall  be  also  set  on  concrete,  as  shown 
by  detail  on  plan,  and  shall  be  set  truly  to  line  and  grade  on  a 
face  batter  of  one  and  a  half  inches  in  its  depth. 

WHEN  SET  ON  SAND.  When  the  pavement  is  to  be  laid  on 
sand  foundation  the  curb  shall  be  firmly  bedded  in  sand  or  fine 
gravel,  and  the  space  behind  the  curb  to  the  top  shall  be  filled 
with  the  same  material  thoroughly  tamped.  In  either  case  each 
curbstone  shall  be  set  truly  to  line  and  grade  on  a  face  batter 
of  one  and  one-half  inches  in  its  depth. 

21.  CHARACTER  OF  CONCRETE.     The  concrete  foundation  for 
curbstone  shall  be  not  less  than  six  (6)  inches  thick  and  seventeen 
(17)  inches  in  width,  and  be  of  the  materials  and  proportions  here- 
inafter described,  except  that  the  broken  stone  shall  be  not  less 
than  one-quarter  (J)  nor  more  than  one  and  a  quarter  (1 J)  inches 
maximum  dimensions;    the  curb  shall  be  immediately  bedded 
on  the  centre  thereof,  with  a  bearing  for  its  full  length  as  soon  as 
the  concrete  is  laid,  and  it  shall  be  at  once  backed  up  with  con- 


ASPHALT   PAVEMENTS  239; 

crete  for  a  width  of  six  (6)  inches,  extending  from  the  bottom  bed 
to  within  four  (4)  inches  of  the  top  of  the  stone.  The  concrete  so 
used  will  be  paid  for  at  the  general  price  per  cubic  yard  for  con- 
crete. 

22.  IN  FRONT  OF  CEMENT  WALK.     When  curb  is  set  in  front 
of  a  monolithic  walk,  the  space  between  the  curb  and  sidewalk 
foundation  shall  be  completely  filled  with  concrete  similar  to  that 
described  above,  to  within  two  (2)  inches  of  the  top;   the  re- 
maining space  to  be  filled  with  Portland  cement  of  the  quality 
hereinafter  specified,  mixed  with  an  equal  part  of  crushed  stone 
used  for  wearing  surface  of  such  walks.     Wherever  curbstones, 
however  set,  shall  have  become  displaced  or  damaged  from  any 
cause,  such  curbstone  shall  be  reset  or  new  ones  shall  be  furnished 
in  their  place  and  no  compensation  therefor  shall  be  allowed. 

23.  SIDEWALKS.     On    repaving    work    the    first    course    of 
flagstones  interfering  with  the  work  of  curb-setting  shall  be  taken 
up  and  relaid  to  the  new  curb  grade,  at  the  expense  of  the  con- 
tractor.    Any  damage  done  by  the  contractor  to  sidewalks  in 
curb-setting,  handling,  or  in  the  storage  of  materials,  shall  be 
made  good  by  him,  at  his  own  expense,  as  shall  be  directed  by  the 
engineer. 

24.  How  LAID.     All  flagging  to  be  relaid  shall  be  firmly  and 
evenly  bedded  to  the  grade  and  pitch  required,  on  three  (3)  inches 
of  steam  ashes  or  sand  free  from  loam  or  clay  and  the  work 
brought  to  an  even  surface,  with  all  joints  close  and  thoroughly 
filled  for  the  full  depth  with  cement  mortar  composed  of  equal 
parts  of  the  best  Portland  cement  and  clean,  sharp  sand,  and  left 
clean  on  the  surface,  and  all  earth,  debris,  and  surplus  material 
shall  be  removed  from  each  block  and  the  sidewalks  swept  clean 
as  soon  as  the  work  thereon  has  been  completed. 

25.  READJUSTMENT  OF  EXTERIOR  FLAGGING.     On  an  original 
improvement  the  contractor  will  be  required  to  relay  at  his  own 
expense  any  and  all  flagstones  adjoining,  but  outside  the  limits 
of  this  work,  which  may  require  readjusting  to  conform  to  the  new 


240  HIGHWAY   ENGINEERING 

grades  and  to  replace  with  new  flagstone  any  such  removed 
stones  which  may  be  broken  in  handling  or  relaying,  as  well  as 
all  flagging  necessarily  removed  in  grading,  unless  a  price  is  asked 
for  the  same. 

26.  QUALITY  AND  DIMENSIONS  OF  NEW  FLAGGING.    All  new 
flagging  shall  be  of  bluestone  of  satisfactory  and  uniform  color 
and  equal  in  quality  to  the  best  North-River  bluestone,  and  shall 
be  free  from  sap,  seams,  flaws,  drill  holes,  and  discolorations.     It 
shall  have  a  smooth  surface,  be  out  of  wind,  and  not  less  than 
three  (3)  inches  thick  at  any  point,  and  shall  be  five  (5)  feet  in 
length  and  not  less  than  two  and  one-half  feet  in  width,  except 
that  wherever  in  sidewalks  an  old  stone  of  superior  dimensions  is 
broken,  but  one  new  stone  shall  be  put  in  its  place,  which  must 
be  in  length  and  width  not  less  than  the  old  stone.     New  flag- 
stone of  smaller  size  shall  be  furnished  when  directed  by  the 
engineer,  such  stone  to  be  of  specification  thickness  and  be  used 
when  necessary  to  match  existing  courses  on  walks  already 
partly  flagged  and  in  the  closure  course  of  such  walks  as  are  to 
be  flagged  for  the  full  width. 

27.  DRESSING  AND  CUTTING.    All  stones  shall  be  chisel- 
dressed  with  opposite  sides  parallel  and  adjacent  sides  at  right 
angles,  on  the  four  (4)  edges  a  distance  down  of  one  (1)  inch  from 
top  and  at  right  angles  thereto,  and  such  dressing  shall  be  entirely 
completed  before  said  stone  shall  be  placed  on  the  bed  prepared. 
Such  further  necessary  dressing  will  be  required  that  the  stones 
may  fit  closely  to  circular  corners  and  coping  courses  and  around 
all  gas  lamps,  posts,  and  poles  of  all  descriptions,  hydrants,  water 
boxes,  sewer  manholes,  basins,  etc.,  and  to  give  openings  nine 
(9)  inches  square  over  city  monuments  and  good  and  sufficient 
openings  around  all  trees. 

28.  LAYING.     All  flagging  shall  be  laid  in  regular  courses  five 
(5)  feet  in  width,  and  shall  be  firmly  and  evenly  bedded  to  the 
grade  and  pitch  required,  on  three  (3)  inches  of  steam  ashes  or 
sand,  free  from  clay  or  loam ;  the  work  to  be  brought  to  an  even 


ASPHALT   PAVEMENTS  241 

surface  with  all  joints  close  and  thoroughly  filled  for  their  full 
depth  with  cement  mortar  composed  of  equal  parts  of  the  best 
quality  of  Portland  cement  and  clean,  sharp  sand,  and  left  clean 
on  the  surface;  but  no  more  mortar  shall  be  mixed  at  any  one 
time  than  can  be  used  within  one-half  (J)  an  hour,  nor  shall  any 
mortar  be  laid  against  any  edge  of  a  stone  until  the  stone  to  abut 
thereagainst  shall  have  been  completely  dressed  ready  for  laying. 

29.  PRICE  TO  INCLUDE.     The  price  paid  per  square  foot  for 
new  flagging  shall  include  the  furnishing  of  the  new  stone  and  all 
work  incidental  to  and  including  its  laying  as  above  described. 

30.  FLAGGING  TO  BE  RELAID.    Where  a  price  is  asked  for 
relaying  old  flagstones,  all  such  existing  stones  which  shall  be 
considered  by  the  engineer  suitable  for  relaying,  or  which,  though 
broken,  may  be  recut  to  an  acceptable  size,  shall  be  pitched  on 
the  four  edges  to  true  lines,  care  being  taken  to  get  a  joint  as 
nearly  at  right  angles  as  possible  to  the  upper  surface  of  the  stone 
and  free  from  feather  edges,  and  be  relaid  in  front  of  the  property 
where  found;   the  stone  to  be  completely  dressed  before  being 
laid  on  the  bed  prepared. 

31.  REMOVAL  OF  FLAGGING.     No  flagstone  whatever  shall  be 
removed  from  its  bed  unless  the  said  stone    shall    have  been 
designated  by  the  engineer  for  removal,  and  said  engineer  or 
inspector  shall  be  present  to  examine  its  condition,  and  it  shall 
be  the  duty  of  the  contractor  to  notify  the  engineer  whenever 
old  flagging  is  to  be  lifted.     All  stones  necessary  to  be  removed 
shall  be  carefully  lifted  by  barring  under  the  exposed  edge,  and 
no  barring  between  joints  shall  be  permitted;  those  in  the  tail 
course  interfering  with  the  work  of  curb-setting  shall  be  lifted 
clear  and  be  set  back.     Flagstones,  on  being  removed,  shall  be 
stood  in  piles  according  to  size  and  be  kept  clear  of  other  material 
(in  front  of  the  property  where  found),  and  when  directed  by  the 
engineer  the  contractor  shall  remove  off  the  work  and  not  again 
re-employ  thereon  any  employee  found  breaking  or  injuring  old 
stone  by  carelessness  in  handling  or  otherwise. 

16 


242  HIGHWAY   ENGINEERING 

32.  HEADING  STONES.     Wherever  the  new  pavement  abuts 
pavement  of  a  different  character  or  an  unpaved  street,  the  con- 
tractor shall  put  down  bluestone  heading  stones  at  least  three  (3) 
feet  long  and  one  (1)  foot  deep,  and  set  with  full  bearing  on  a  bed 
of  concrete  nine  (9)  inches  wide  and  six  (6)  inches  deep,  of  the 
quality  hereinafter  described.     These  heading  stones  shall  be  of 
good  sound  bluestone,  free  from  lamination  or  seam;  they  shall  be 
dressed  square  on  top  to  a  good  surface,  free  from  great  irregulari- 
ties, and  to  a  uniform  width  of  not  less  than  four  and  a  half 
(4J)  inches.     The  ends  shall  be  jointed  square  down  to  give  close 
joints,  and  the  bottoms  shall  be  nowhere  less  than  three  (3)  inches 
wide  and  be  cut  to  give  a  full  square  bearing  throughout,  and  the 
sides  shall  be  free  from  bunches. 

33.  CONCRETE. — CEMENT. — PROPORTION.    The  concrete  shall 
be  made  of  the  best  quality  of  Portland  cement,  samples  of  which 
must  be  submitted  at  least  ten  (10)  days  (Sundays  and  holi- 
days excluded)  before  using,  for  the  inspection  and  approval  of 
the  chief  engineer.  All  cement  shall  be  a  uniform  quality,  color, 
and  weight,  and  briquettes  of  one  (1)  square  inch  section  shall 
develop  or  exceed  the  following  tensile  strength : 

Neat — four  (4)  hours  in  moist  air,  twenty  (20)  hours 

in  water 200  pounds 

Neat — one  (1)  day  in  air,  six  (6)  days  in  water 400  pounds 

One  (1)  of  cement,  three  (3)  of  sand,  one  (1)  day  in 

air,  six  (6)  days  in  water 150  pounds 

The  concrete  shall  be  composed  of  one  (1)  part  of  cement,  three 
(3)  parts  of  sand,  and  six  (6)  parts  of  broken  stone.  The  unit  of 
measure  shall  be  the  barrel  of  cement  as  packed  by  and  received 
from  the  manufacturer. 

34.  SAND  AND  STONE.     The  sand  shall  be  clean,  coarse,  and 
sharp,  and  be  free  from  loam  or  dirt.     The  broken  stone  shall  be 
of  trap,  granite,  or  limestone  or  such  other  stone  taken  from  the 
line  of  work  as  shall  be  satisfactory  in  the  judgment  of  the  engi- 
neer.    It  shall  be  entirely  free  from  dust  and  dirt,  and  be  of 


ASPHALT   PAVEMENTS  243 

graded  sizes  such  that  all  will  pass  through  a  revolving  circular 
screen  having  holes  two  and  one-half  (2J)  inches  in  diameter  and 
be  retained  by  a  screen  having  holes  one-half  ( J)  inch  in  diameter. 
The  sand  and  stone  shall  be  placed  upon  board  platforms  and  be 
kept  free  from  dirt,  and  the  cement  shall  be  properly  blocked  up 
and  protected  from  dampness. 

35.  MIXING.     The  sand  and  cement  shall  be  mixed  dry,  then 
made  into  mortar  by  the  addition  of  water,  when  the  broken  stone 
shall  be  added  and  the  whole  mass  thoroughly  mixed.     The  con- 
crete shall  then  be  spread  upon  the  subgrade  and  rammed  so  as 
to  fill  all  the  voids  of  the  stone  with  mortar  and  bring  the  surface 
exactly  three  (3)  inches  below  the  finished  pavement.     If  a 
machine  be  used  for  mixing,  the  above  operation  may  be  varied 
as  may  be  required.     No  concrete  shall  be  used  that  has  been 
mixed  more  than  one-half  hour.    The  concrete  shall  be  protected 
from  the  weather  when  deemed  necessary  by  the  engineer. 

36.  No  CARTING.     No  horses,  carting,  or  wheeling  shall  be 
allowed  on  the  concrete  before  the  same  has  set,  except  on  planks 
furnished  and  laid  by  the  contractor. 

37.  THICKNESS.     The  concrete  foundations  shall  be  five  (5) 
inches  thick,  except  where  otherwise  specially  ordered. 

STONE   PAVEMENTS 

38.  BRIDGESTONES. — QUALITY.     When  required,  old  bridge- 
stones  shall  be  redressed,  rejointed,  and  relaid  as  hereafter  di- 
rected for  new  bridgestones,  and  for  such  purpose  shall  be  hauled 
to  the  necessary  point  or  points  by  the  contractor.    Bridgestone 
broken  by  being  so  hauled,  redressed,  or  relaid  shall  be  replaced 
by  the  contractor  at  his  own  expense.     New  bridgestones  shall 
be  of  the  same  quality  of  granite  as  the  blocks,  free  from  all  im- 
perfections. 

39.  DIMENSIONS.     They  shall  be  eighteen  (18)  inches  wide, 
of  a  uniform  thickness,  not  less  than  six  or  more  than  eight  inches 
in  depth,  and  from  three  and  one-half  (3J)  to  eight  (8)  feet  in 


244  HIGHWAY   ENGINEERING 

length,  except  that  in  special  cases,  between  railroad  tracks, 
they  may  be  of  such  dimensions  as  may  be  approved  by  the  chief 
engineer  of  the  Bureau  of  Highways. 

40.  DRESSING.    The  top  shall  be  dressed  to  a  surface  not 
varying  in  evenness  more  than  one-quarter  (J)  of  an  inch.     The 
sides  and  ends  shall  be  dressed  square  down  and  the  latter  cut  to 
a  transverse  bevel  of  six  (6)  inches  in  the  width  or  to  such  other 
bevel  as  may  be  directed,  and  the  jointing  from  top  to  bottom 
shall  give  joints  not  greater  than  one-quarter  (J)  of  an  inch. 

41.  LAYING.    The  bridgestones  shall  be  laid  in  parallel  courses 
separated  by  granite  blocks,  and  shall  be  well  and  firmly  bedded 
on  a  layer  of  sand  spread  on  the  foundation  as  prepared  for  the 
pavement.     The  transverse  joints  shall  be  broken  by  a  lap  of  at 
least  one  (1)  foot,  and  be  so  laid  as  not  to  be  parallel  to  vehicu- 
lar traffic. 

42.  BLOCKS.     The  blocks  to  be  used  shall  be  of  a  durable, 
sound,  and  uniform  quality  of  granite,  each  stone  measuring  not 
less  than  eight  (8)  inches  nor  more  than  twelve  (12)  inches  in 
length,  not  less  than  three  and  one-half  (3J)  nor  more  than  four 
and  one-half  (4J)  inches  in  width,  and  not  less  than  seven  (7)  nor 
more  than  (8)  inches  in  depth,  and  the  stones  shall  be  of  the  same 
quality  as  to  hardness,  color,  and  grain.  No  outcrop,  soft,  brittle, 
or  laminated  stone  will  be  accepted.     The  blocks  are  to  be  rec- 
tangular on  top  and  sides,  uniform  in  thickness,  to  lay  closely, 
and  with  fair  and  true  surfaces,  free  from  bunches.     Over  special 
constructions,  the  blocks  may  be  of  dimensions  other  than  above 
specified  when  approved  by  the  engineer.     The  stone  from  each 
quarry  shall  be  piled  and  laid  separately  in  different  sections  of 
the  work,  and  in  no  case  shall  the  stones  from  different  quarries 
be  mixed . 

43.  PAVING  CEMENT.     The  paving  cement  to  be  used  in  filling 
the  joints  between  and  around  the  paving  blocks  and  bridgestones 
when  laid  on  concrete,  as  hereafter  provided,  shall  be  composed 
of  twenty  (20)  parts  of  refined  asphalt  and  three  (3)  parts  of 


ASPHALT   PAVEMENTS  245 

residuum  oil,  mixed  with  one  hundred  (100)  parts  of  coal-tar 
pitch  such  as  is  ordinarily  numbered  four  (4)  at  the  manufactory, 
the  proportions  to  be  determined  by  weight.  The  pitch,  oil,  and 
asphalt  must  be  heated  and  mixed  on  the  work  in  the  proportions 
named,  as  needed  for  immediate  use  unless  otherwise  directed. 

44.  SAND.     On  the  roadbed  or  on  the  concrete  foundation,  as 
designated,  shall  be  laid  a  bed  of  clean,  coarse  dry  sand  to  such 
depth  (in  no  case  less  than  one  and  a  half  [1J]  inches),  as  may  be 
necessary  to  brmg  the  surface  of  the  pavement,  when  thoroughly 
rammed,  to  the  proper  grade. 

45.  LAYING.    On  this  sand  bed,  and  to  the  grade  and  crown 
specified,  shall  be  laid  the  stone  blocks  at  right  angles  to  the  line 
of  the  street  or  at  such  angle  as  may  be  directed.     Each  course 
of  blocks  shall  be  laid  straight  and  regularly,  with  the  end  joints 
by  a  lap  of  at  least  three  (3)  inches,  and  in  no  case  shall  stone  of 
different  width  be  laid  in  the  same  course  except  on  curbs.     All 
joints  shall  be  close  joints,  except  that  when  gravel  filling  is  used 
the  joints  between  courses  shall  be  not  more  than  three-quarters 
(I)  of  an  inch  in  width. 

46.  ON  SAND  FOUNDATION.    As  the  blocks  are  laid  they  shall 
be  covered  with  sharp,  coarse  sand,  free  from  gravel,  which  shall 
be  raked  or  brushed  until  all  the  joints  become  filled  therewith; 
the  blocks  shall  then  be  thoroughly  rammed  to  a  firm,  unyielding 
bed,  with  a  uniform  surface  to  conform  to  the  grade  and  crown  of 
the  street.     It  shall  be  covered  with  a  good  and  sufficient  second 
coat  of  clean,  sharp  sand,  and  shall  immediately  thereafter  be 
thoroughly  rammed  until  the  work  is  made  solid  and  secure;  and 
so  on  until  the  whole  of  the  work  shall  have  been  well  and  faith- 
fully completed.    No  truck  or  vehicle  shall  be  allowed  to  pass 
over  it  until  the  final  ramming  has  been  completed   as  above, 
but  no  ramming  shall  be  done  within  twenty  feet  of  the  face  of 
the  work  that  is  being  laid. 

47.  ON  CONCRETE  FOUNDATION.    When  the  pavement  is  laid 
on  a  concrete  foundation  the  blocks  shall  be  covered  with  a  clean, 


246  HIGHWAY   ENGINEERING 

hard,  and  dry  gravel,  which  shall  have  been  artificially  heated  and 
dried  in  proper  appliances,  placed  in  close  proximity  to  the  work, 
the  gravel  to  be  brushed  in  until  all  the  joints  are  filled  therewith 
to  within  three  (3)  inches  of  the  top.  The  gravel  must  be  en- 
tirely free  from  sand  or  dirt,  and  must  have  passed  through  a 
sieve  of  five-eighth  (f )  inch  mesh  and  been  retained  by  a  three- 
eighth  (|)  inch  mesh. 

48.  RAMMING.     The  blocks  must  then  be  thoroughly  rammed 
and  the  ramming  repeated  until  they  are  brought  to  an  unyield- 
ing bearing  with  a  uniform  surface,  true  to  the  given  grade  and 
crown.     No  ramming  shall  be  done  within  twenty  (20)  feet  of  the 
face  of  the  work  that  is  being  laid. 

49.  TEMPERATURE  OF  PAVING  CEMENT.     The  boiling  paving 
cement,  heated  to  a  temperature  of  300°  Fahrenheit,  and  of  the 
composition  hereinbefore  described,  shall  then  be  poured  into 
the  joints  until  the  same  are  full,  and  remain  full  to  the  top  of 
the  gravel.     Hot  gravel  shall  then  be  poured  along  the  joints 
until  they  are  full  flush  with  the  top  of  the  blocks,  when  they  shall 
again  be  poured  with  the  paving  cement  till  all  voids  are  com- 
pletely filled. 

50.  The  appliances  for  heating  paving  cement  shall  be  suf- 
ficient in  number  and  of  such  efficiency  as  will  permit  the  pourers 
to  closely  follow  the  back  rammers,  and  all  joints  of  the  finally 
rammed  pavement  shall  have  been  filled  with  paving  cement  as 
above  noted,  before  the  cessation  of  the  work  for  the  day  or  any 
other  cause. 

51.  TOOTHING  CEMENT.    When  shown  on  the  plans  on  either 
or  both  sides  of  the  rails  of  car  tracks,  as  may  be  designated,  the 
contractor  shall  lay  on  the  concrete  foundation  adjacent  thereto 
a  bed  of  Portland-cement  mortar,  of  the  quality  hereinbefore  set 
forth,  one  of  cement  to  three  of  sand,  in  which  long  and  short 
blocks,  alternating  and  toothing  into  the  pavement  as  headers, 
shall  be  bedded.     This  mortar  bed  shall  extend  outward  from 
the  rail  to  a  width  of  four  (4)  inches  beyond  the  outer  edge  of 


ASPHALT   PAVEMENTS  247 

the  long  blocks,  and  it  shall  not  be  prepared  for  or  laid  to  an 
extent  greater  than  fifteen  (15)  feet  in  advance  of  the  pavers,  and 
before  laying  the  concrete  shall  have  been  first  thoroughly 
swept  and  wetted. 

52.  The  top  of  concrete  shall  be  at  such  elevation  and  the 
mortar  shall  be  of  such  thickness  (hi  no  case  less  than  1 J  inches) 
that  when  the  paving  blocks  are  therein  embedded  there  shall 
remain  at  least  one  inch  of  mortar  under  the  stone,  the  top  sur- 
face shall  be  a  quarter  of  an  inch  above  the  tread  of  the  adjacent 
rail  (except  at  guards  or  other  projections,  when  they  will  be 
flush  with  the  latter),  and  the  bottom  of  the  stone  shall  be  locked 
in  a  position  by  the  displaced  mortar  rising  in  the  joints. 

53.  No  ramming  of  toothing  stones  shall  be  allowed,  and 
they  shall  be  set  carefully  to  grade,  with  joints  filled  and  poured 
as  above,  except  that  smaller  joints  and  finer  gravel  may  be  used 
when  deemed  best  by  the  engineer.     These  toothing  stones  shall 
be  properly  protected  until  the  mortar  is  set. 

54.  Whenever  granite  blocks  are  laid  in  connection  with  an 
asphalt  pavement  the  work  shall  be  done  in  accordance  with  the 
above  specifications. 

ASPHALT   PAVEMENT 

55.  DEFINITION.    The  pavement  proper  shall  consist  of  a 
binder  course  one  (1)  inch  in  thickness  and  a  wearing  surface 
two  (2)  inches  thick  and  equal  to  the  pavement  mixture  herein- 
after described.     Before  laying  binder,  the  surface  of  the  founda- 
tion shall  be  thoroughly  swept  and  cleaned,  and  all  dirt  and  fine 
particles  removed,  from  the  joints  of  blocks  to  such  a  depth  as 
may  be  directed  by  the  engineer. 

56.  BINDER  COURSE.     The  binder  shall  be  composed  of  suit- 
able clean  broken  stone  passing  a  one-and-a-quarter  (1J)  inch 
screen,  not  more  than  ten  (10)  per  cent  of  which  shall  pass  a 
No.  10  screen. 

57.  STONE.     The  stone  shall  be  heated  in  suitable  appliances, 


248  HIGHWAY   ENGINEERING 

not  higher  than  325°  Fahrenheit,  and  then  thoroughly  mixed  by 
machinery  with  asphaltic  cement  equivalent  in  composition  to 
that  hereinafter  set  forth,  at  300°  to  325°  Fahrenheit,  in  such 
proportion  as  shall  be  acceptable  to  the  engineer. 

58.  LAYING.     The  binder  must  be  hauled  to  the  work  and 
spread  while  hot  upon  the  foundation  to  such  thickness  that,  after 
being  immediately  compacted  by  ramming  and  rolling  until  it  is 
cold,  its  depth  shall  be  at  no  place  less  than  one  (1)  inch,  and  its 
upper  surface  shall  be  parallel  to  the  surface  of  the  pavement  to 
be  laid.     Upon  this  binder  course  must  be  laid  the  wearing  sur- 
face or  pavement  proper. 

59.  PAVEMENT  MIXTURE.     The  pavement  mixture  for  the 
wearing  surface  shall  be  composed  of : 

(a)  Asphaltic  cement  (refined  asphalt,  heavy  petroleum  oil, 
or  liquid  asphalt). 

(b)  Clean,  sharp  sand. 

(c)  Finely  powdered  inorganic  dust. 

60.  DEFINITION.     The  term  asphalt  shall  be  construed  to 
signify  any  natural  mineral  bitumen,  liquid  or  solid,  which  is  ad- 
hesive, viscous,  ductile,  and  elastic,  or  which  becomes  adhesive, 
viscous,  ductile,  and  elastic  on  the  application  of  heat.     Said 
natural  bitumen  may  be  either  in  a  state  of  purity  or  in  ad- 
mixture with  native,  non-bituminous  matter. 

61.  COMPOSITION.     The  refined  asphalt  shall  be  obtained  by 
refining  crude  natural  asphalt  until  the  product  is  homogeneous 
and  free  from  water.    Asphalt  obtained  from  the  distillation  of 
asphaltic  oils  will  not  be  accepted.     It  must  not  be  affected  by 
the  action  of  water;  must  contain  not  less  than  ninety  (90)  per 
cent  of  bitumen  soluble  in  carbon  bisulphide,  and  of  the  bitumen 
thus  soluble  in  carbon  bisulphide  not  less  than  sixty-eight  (68) 
per  cent  shall  be  soluble  in  boiling  Pennsylvania  pertroleum 
naphtha  (boiling-point  from  40  to  60  centigrade) ;  or,  if  it  does 
not  contain  sixty-eight  (68)  per  cent  thus  soluble  in  naphtha, 
but  is  satisfactory  in  other  respects,  the  deficiency  may  be  sup- 


ASPHALT   PAVEMENTS  249 

plied  by  fluxing  the  refined  asphalt,  with  such  a  percentage 
of  a  viscous  liquid  asphalt,  satisfactory  to  the  engineer,  as 
will  bring  it  up  to  the  required  standard.  It  must  comply  in 
all  respects  with  the  tests  enumerated  in  a,  b,  c,  d,  and  e  of 
Paragraph  62. 

62.  PETROLEUM  OIL.     Heavy  petroleum  oil,  if  used  in  the 
manufacture  of  the  asphaltic  cement  as  hereinafter  described, 
shall  be  a  petroleum  from  which  the  lighter  oils  have  been  re- 
moved by  distillation  without  cracking,  until  it  has  a  specific  grav- 
ity of  15°  to  22°  Beaume  and  the  following  properties : 

REQUIREMENTS,  (a)  Flash  test  not  less  than  300°  Fahren- 
heit (the  flash  test  shall  be  taken  in  a  New  York  State  closed 
oil-tester) . 

(b)  Fire  test  not  less  than  350°  Fahrenheit. 

(c)  No  appreciable  amount  of  light  oils  or  matter  volatile 
under  250°  Fahrenheit. 

(d)  Matter  volatile  at  350°  Fahrenheit  in  24  hours,  less  than 
8  per  cent.  (The  test  for  "  matter  volatile  at  350°  Fahrenheit  " 
shall  be  made  with  approximately  50  gms.  of  oil,  in  an  open,  flat- 
bottom,  cylindrical  dish  2^  ins.  in  diameter  and  If  ins.  high. 
The  thermometer  shall  be  applied  so  as  to  register  the  tempera- 
ture of  the  oil.) 

(e)  It  shall  be  free  from  coke  and  any  manner  or  form  of 
adulteration. 

63.  LIQUID  ASPHALT.     Liquid  asphalt,  maltha,  or  any  other 
softening  agent  fulfilling  the  above  test  and  approved  by  the 
engineer,  may  be  used  in  place  of  heavy  petroleum  oil. 

64.  ASPHALTIC  CEMENT.     When  refined  asphalt  is  not  already 
of  the  proper  consistency  an  asphaltic  cement  shall  be  prepared 
by  fluxing  refined  asphalt  with  heavy  petroleum  oil  or  other  ap- 
proved softening  agent,  complying  with  the  above  specifications, 
at  a  temperature  between  250°  and  350°  Fahrenheit  and  in  such 
proportion  as  to  produce  an  asphaltic  cement  of  a  consistency 
to  be  determined  by  the  engineer.    The  asphaltic  cement  shall 


250  HIGHWAY   ENGINEERING 

fulfil  the  requirements  of  paragraphs  a,  b,  c,  d,  and  e  of  Section 
62  above. 

65.  As  soon  as  the  fluxing  agent  is  added  the  entire  mass  shall 
be  agitated  by  an  air  blast  or  other  suitable  appliance,  and  the 
agitation  continued  until  a  homogeneous  cement  is  produced. 
The  asphaltic  cement  must  never  be  heated  to  a  temperature  ex- 
ceeding 350°  Fahrenheit.     If  asphaltic  cement  containing  over 
ten  per  cent  of  foreign  material  is  kept  in  storage,  it  must  be 
thoroughly  agitated  when  used,  as  must  also  all  dipping  kettles 
while  in  use. 

66.  SAND.     The  sand  to  be  used  shall  be  hard-grained,  moder- 
ately sharp  and  clean,  not  containing  more  than  1  per  cent  of 
clay  or  loam.     On  sifting  the  whole  shall  pass  a  10  mesh  screen, 
20  per  cent  shall  pass  an  80  mesh  screen,  and  at  least  7  per  cent 
shall  pass  a  100  mesh  screen. 

67.  INORGANIC  DUST. — The  inorganic  dust  shall  be  finely 
powdered  carbonate  of  lime,  granite,  quartz,  or  other  inorganic 
dust  approved  by  the  engineer.     Such  inorganic  dust  must  be  of 
such  a  degree  of  fineness  that  the  whole  of  it  shall  pass  a  30  mesh 
screen,  and  at  least  66  per  cent  a  200  mesh  screen. 

68.  PAVEMENT  MIXTURE.     The  materials  complying  with  the 
above  specifications  shall  be  mixed  in  proportions  by  weight, 
depending  upon  their  character.     These  proportions  will  be  de- 
termined by  the  engineer,  but  the  percentage  of  matter  soluble  in 
carbon  bisulphide  in  any  pavement  mixture  shall  not  be  less  than 
nine  and  one-half  nor  more  than  twelve  per  cent.     If  the  pro- 
portions of  the  mixtures  are  varied  in  any  manner  from  those 
specified,  the  mixture  will  be  condemned,   its  use  will  not  be 
permitted,  and,  if  already  placed  on  the  street,  it  will  be  removed 
and  replaced  by  proper  materials  at  the  expense  of  the  contractor. 

69.  The  sand  and  the  asphaltic  cement  will  be  heated  sepa- 
rately to  approximately  325°  Fahrenheit.  The  stone  dust  shall  be 
mixed,  while  cold,  with  the  hot  sand.     The  asphaltic  cement  will 
then   be  mixed  with  the  sand  and  stone  dust,  at  the  required 


ASPHALT   PAVEMENTS  251 

temperature  and  in  the  proper  proportion  in  a  suitable  apparatus, 
so  as  to  effect  a  thoroughly  homogeneous  mixture.  Sand  boxes 
and  asphalt  gauges  shall  be  weighed  in  the  presence  of  inspectors 
as  often  as  may  be  desired,  and  samples  of  any  of  the  materials 
used  shall  be  supplied  to  the  inspector  of  asphalt  at  any  time, 
and  the  engineer  or  his  representative  shall  have  access  to  all 
branches  of  the  work  at  any  time. 

70.  LAYING  THE  PAVEMENT.     The  above-described  materials 
shall  be  mixed  in  the  determined  proportions  in  a  standard  as- 
phalt-mixer and  carried  to  the  street  at  a  temperature  ranging 
from  250°  to  325°  Fahrenheit  and  spread  upon  the  binder  to  such 
a  depth  as  will  insure  a  thickness  of  two  (2)  inches  after  ultimate 
compression.     This  compression  will  be  attained  by  first  smooth- 
ing the  surface  with  a  hand  roller,  or  a  light  steam  roller,  after 
which  hydraulic  cement  shall  be  swept  over  it,  when  the  rolling 
will  be  continued  with  a  ten  ton  roller  until  no  impression  is 
made  upon  the  surface.     A  space  of  twelve  (12)  inches  next  the 
curb  shall  be  coated  with  asphaltic  cement  and  the  same  ironed 
into  the  pavement  with  hot  smoothing  irons. 

71.  ROCK  ASPHALT. — Should  any  of  the  rock  asphalts  be  used, 
the  material  shall  be  a  natural  bituminous  limestone  or  sandstone 
or  a  mixture  of  the  two,  and  shall  be  prepared  and  laid  in  the 
following  manner:  The  lumps  of  rock,  after  being  mixed  in  the 
proper  proportions,  shall  be  finely  crushed  and  pulverized,  and 
the  powder  passed  through  a  twenty  (20)  mesh  sieve.     In  case 
of  the  use  of  any  asphaltic  limestone,  or  of  a  mixture  of  an  asphal- 
tic limestone  and  an  asphaltic  sandstone,  nothing  whatever  shall 
be  added  to  or  taken  from  the  powder  obtained  by  grinding  the 
natural  bituminous  rock.     Should  it  be  proposed  to  use  an  as- 
phaltic sandstone  only,  which  contains  more  than  nine  (9)  per 
cent  of  natural  bitumen,  of  such  a  consistency  that  the  resulting 
pavement  would  prove  too  soft  to  sustain  traffic,  the  material, 
if  satisfactory  in  other  respects,  shall  be  made  to  conform  with 
the  requirements  of  Section  73,  by  the  addition  of  inorganic 


252  HIGHWAY   ENGINEERING 

dust;  in  such  manner  and  in  such  proportion  as  the  engineer  may 
direct.  The  powder  shall  contain  from  nine  (9)  to  twelve  (12) 
per  cent  of  natural  bitumen. 

72.  LAYING.     This  powder  shall  be  heated  in  a  suitable  ap- 
paratus to  200°  or  250°  Fahrenheit  and  must  be  brought  to  the 
ground  at  a  temperature  of  not  less  than  180°  Fahrenheit  in  carts 
made  for  the  purpose,  and  carefully  spread  as  specified  for  re- 
fined asphalt  pavement,  to  such  a  depth  that  after  having  re- 
ceived its  ultimate  compression  it  will  have  a  thickness  of  two 
and  one-half  (2J)  inches  when  laid  on  concrete.     When  the 
foundation  is  other  than  concrete  it  shall  be  laid  on  a  one  inch 
binder  course  as  heretofore  described,  and  the  net  thickness  of 
the  rock  asphalt  wearing  surface  after  compression  shall  be  two 
(2)  inches.     The  surface  shall  be  rendered  perfectly  even  by 
tamping,  smoothing,  and  rolling  with  heated  appliances  of  ap- 
proved design. 

73.  GENERAL  REQUIREMENTS.    The  materials  complying  with 
the  above  specifications  shall  be  mixed  in  such  proportions  and 
within  such  limits,  by  weight,  depending  on  their  character,  as 
shall  be  determined  by  the  engineer,  but  whatever  may  be  the 
character  of  the  asphalt  or  of  the  asphaltic  cement  used,  the 
pavement  obtained  must  and  shall  conform  to  the  following  gen- 
eral requirements :  The  pavement  when  laid  shall  not  be  so  soft 
as  to  be  unfit  for  travel  on  the  hottest  days  of  summer,  nor  so  hard 
as  to  disintegrate  from  the  effect  of  frost.     It  shall  contain  no 
water  nor  appreciable  amount  of  light  oils,  nor  matter  volatile  at 
a  temperature  of  250°  Fahrenheit.     When  laid  the  wearing 
surface  mixture  shall  yield  not  less  than  nine  and  one-half  (9J) 
nor  more  than  twelve  (12)  per  cent  (except  in  the  case  of  rock 
asphalt,  when  the  limit  shall  be  as  established  in  Section  71)  of 
bitumen  soluble  in  carbon  bisulphide,  of  which  bitumen  not  less 
than  sixty-eight  (68)  per  cent  shall  be  soluble  in  boiling  Penn- 
sylvania petroleum  naphtha,  boiling-point  of  40°  to  60°  centi- 
grade.    All  of  the  mineral  matter  shall  pass  a  10  mesh  per  linear 


ASPHALT    PAVEMENTS  253 

inch  sieve,  and  not  less  than  18  per  cent  shall  pass  a  100  mesh 
per  linear  inch  sieve,  while  the  remainder  shall  be  graduated 
between  these  limits.  If  rock  asphalt  be  used  the  same  shall  be 
laid  in  accordance  with  Section  72. 

74.  In  case  of  repairs  it  shall  be  required  that  such  repairs  be 
made  with  a  pavement  mixture  equal  to  the  above  described. 

75.  No  ASPHALT  TO  BE  LAID  IN  WET  WEATHER.     No  asphalt 
shall  be  laid  during  wet  weather,  or  unless  the  surface  of  the 
foundation  is  perfectly  dry.     All  materials,  as  well  as  the  plant 
and  methods  of  manufacture,  shall  be  subject  at  all  times  to  the 
inspection  and  approval  of  the  chief  engineer  of  the  Bureau  of 
Highways  or  of  such  engineer  or  inspectors  as  may  be  in  charge 
of  the  work. 

76.  APPROACHES.     The  curbstones,  crosswalks,  and  gutters 
of  the  adjoining  pavements  and  all  pavements  abutting  the  new 
work  shall  be  readjusted  and  brought  to  the  new  grades  and  lines 
to  the  extent  deemed  necessary  by  the  engineer,  and  such  read- 
justment of  curb  and  pavement  shall  include  rejointing,  resetting, 
and  relaying  as  hereinbefore  provided,  at  the  prices  stipulated. 

77.  CLEARING  UP.    All  surplus  materials,  earth,  sand,  rub- 
bish, and  stones,  except  such  stones  as  are  retained  by  order  of 
the  engineer,  are  to  be  removed  from  the  line  of  the  work,  block 
by  block,  as  rapidly  as  the  work  progresses.     All  material  cover- 
ing the  pavement  and  sidewalks  shall  be  swept  into  heaps  and 
immediately  removed  from  the  line  of  the  work. 

78.  During  the  prosecuting  of  the  work  the  contractor  shall 
keep  the  footway  clean  by  sweeping.    When  material  is  removed 
the  sidewalk  must  be  immediately  swept  clean  by  the  contractor, 
and  when  public  or  local  inconvenience  is  caused  by  dust  the  con- 
tractor shall  water  any  piles  or  surface  of  earth  or  the  sidewalks, 
or  pavement  foundation  during  sweeping  when  and  where  neces- 
sary or  whenever  required  by  the  engineer  to  do  so.     The  con- 
tractor must  remove  all  stains  or  deposits  of  bitumen  from  side- 
walks and  adjoining  pavements. 


254  HIGHWAY  ENGINEERING 

THE  CITY  OF  NEW  YORK,  OFFICE  OF  THE  PRESIDENT  OF  THE 
BOROUGH   OF   MANHATTAN,    BUREAU   OF   HIGHWAYS. 

Specifications  for  Regulating,  Grading,  and  Paving  or  Repairing  with 

Asphalt-Block  Pavement  on  a Foundation  the  Roadway 

of from to together    with     all    Work    In- 
cidental thereto. 

1.  EXTENT  OF  WORK.     This  shall  consist  of  (1)  taking  up  the 
necessary  curb,  bridgestone,  and  such  portions  of  the  pavement 
that  may  be  required  to  be  removed  for  the  proper  laying  of  the 
pavement;  (2)  excavating  the  necessary  portions  of  the  roadway 
of  subsoil,  rock,  or  masonry  where  the  same  is  above  the  proper 
subgrade  or  where  the  material  underlying  is  not  of  proper  char- 
acter; (3)  filling  in  depressions  or  openings  in  the  roadway  wher- 
ever said  depressions  are  below  the  grade  aforesaid  or  have  been 
caused  by  the  removal  of  improper  material;  (4)  laying  concrete 
as  a  foundation,  as  has  been  designated;    (5)  resetting  catch- 
basins  and  resetting  or  furnishing  and  setting  city  manhole  heads 
to  grade;  (6)  furnishing  and  setting  and  redressing  and  resetting 
the  necessary  curbstones  and  heading  stones,  as  required;    (7) 
furnishing  all  the  materials  for,  and  laying  an  asphalt-block 
pavement  in  the  roadway;    (8)  readjusting  and  relaying  pave- 
ment and  resetting-  curbstones  in  the  approaches  of  intersecting 
streets  and  avenues;  all  to  be  in  accordance  with  the  plan  and 
profile  of  the  said  street,  now  on  file  in  the  Bureau  of  Highways, 
with  workmanship  and  materials  equalling  in  every  respect  the 
requirements  of  these  specifications  and  the  samples  accepted. 

2.  Material  furnished  and  work  done  not  in  accordance  with 
these  specifications,  in  the  opinion  of  the  engineer,  shall  be  im- 
mediately removed  and  so  replaced  or  corrected  as  to  be  in  ac- 
cordance therewith. 

3.  ESTIMATE  OF  QUANTITIES.    The  estimates  of  the  engineer 
of  the  quantity  and  quality  of  the  supplies  required,  and  the 


ASPHALT   PAVEMENTS  255 

nature  and  the  extent,  as  near  as  possible,  of  the  work,  are  herein 
stated  and  set  forth. 

: square  yards  of  asphalt-block  pavement. 

cubic  yards  of  concrete,  including  mortar  bed. 

' linear  feet  of  new  curbstone,  furnished  and  set. 

linear  feet  of  old  curbstone  redressed,  rejoin  t- 

ed,  and  reset. 
noiseless  covers,  complete,  for  water  manholes, 

to  be  furnished  and  set. 
noiseless  covers,  complete,  for  sewer  manholes, 

to  be  furnished  and  set. 

4.  PEKSONAL  EXAMINATION  OF  WORK.    Bidders  must  satisfy 
themselves  by  personal  examination  of  the  location  of  the  pro- 
posed work,  and  by  such  other  means  as  they  may  prefer,  as  to 
the  accuracy  of  the  foregoing  statement,  and  they  shall  not,  at  any 
time  after  the  submission  of  their  bid,  dispute  or  complain  of  such 
statement  or  estimate  of  the  engineer,  nor  assert  that  there  was 
any  misunderstanding  in  regard  to  the  nature  or  amount  of  the 
work  to  be  done. 

5.  WORK  TO  COMMENCE  ONLY  WHEN  ORDERED  ON.    No  work 
will  be  paid  for  which  is  done  before  the  contractor  is  ordered  to 
proceed. 

6.  PROSECUTION  OF  WORK.    The  work  under  this  contract 
shall  be  prosecuted  at  and  from  as  many  different  points,  at  such 
times  and  in  sections  of  such  length  along  the  line  of  the  work,  and 
with  such  force  as  the  president  may,  from  time  to  time,  during 
the  progress  of  the  work,  determine,  at  each  of  which  points  in- 
spectors may  be  placed  to  supervise  the  same. 

7.  MATERIAL  NOT  TO  OBSTRUCT  TRAVEL.    During  suspensions 
all  materials  delivered  upon,  but  not  placed  in  the  work,  shall 
be  neatly  piled  so  as  not  to  obstruct  public  travel,  or  shall  be 
removed  from  the  line  of  the  work  at   the  direction  of  the 
engineer,  and   unless   the   materials   be   so   removed  by    the 
contractor  upon  notice  from  the  engineer,  the  materials  may 


256  HIGHWAY   ENGINEERING 

be  removed  by  the  president  and  the  expense  thereof  charged  to 
the  contractor. 

8.  ENCUMBRANCES.   The  contractor  shall  remove  at  his  own 
expense,  when  directed  by  the  engineer,  any  encumbrances  or 
obstructions  on  the  line  of  the  work,  located  or  placed  there  prior 
to  or  after  its  commencement. 

9.  CONTRACTOR  NOT  TO  DISTURB  CITY  MONUMENTS.    The 
contractor  shall  not  excavate  around  such  city  monuments  and 
bench-marks  as  may  come  within  the  limits  of  or  be  disturbed  by 
the  work  herein  contemplated  nearer  than  five  (5)  feet  or  in  any 
manner  disturb  the  same,  but  shall  cease  work  at  such  locations 
until  the  said  monuments  or  marks  have  been  referenced  and 
reset  or  otherwise  disposed  of  by  the  president.     The  necessary 
labor  to  remove,  care  for,  and  reset  all  such  monuments  and  bench- 
marks shall  be  furnished  without  charge  therefor  by  the  con- 
tractor. 

10.  MANHOLES,  ETC.,  TO  BE  RESET.     Such  catch-basins,  man- 
hole frames  and  heads  for  sewers,  water  pipes  or  other  conduits 
belonging  to  the  City  on  the  line  of  the  work  as  may  be  designated 
shall  be  reset  to  the  new  grades  and  lines  by  the  contractor  with- 
out extra  charge  therefor;   and  they  shall  be  brought  to  such 
grades  with  brick  masonry  of  the  same  thickness  as  that  originally 
used,  laid  in  hydraulic  cement  mortar,  and  the  cost  thereof  shall 
be  included  in  the  price  bid  for  the  contiguous  pavement. 
Noiseless  covers,  complete,  with  interchangeable  ventilating  and 
non-ventilating  fittings,  for  water  and  sewer  manholes,  of  the 
design  approved  by  the  engineer,  shall  be  furnished  and  set 
when  required,  in  the  manner  above  designated,  the  cost  of  same 
to  be  included  in  the  price  bid  per  square  yard  for  completed 
asphalt-block  pavement.    All  other  manholes  and  boxes  are  to 
be  reset  to  the  proper  grade,  under  the  contractor's  direction,  by 
the  companies  owning  the  same. 

11.  The  grades  of  all  manholes  and  boxes  must  conform  ab- 
solutely to  that  of  the  pavement  surrounding,  and  the  contractor 


ASPHALT   PAVEMENTS  257 

shall  supervise  and  see  that  all  such  resetting  is  substantially 
and  accurately  done  in  conformity  with  the  foregoing,  whether 
such  resetting  shall  be  done  by  his  own  men  or  by  those  from 
other  companies,  and  he  shall  report  in  writing  to  the  engineer 
any  disinclination  or  negligence  on  the  part  of  the  latter  to  per- 
form their  work  properly. 

12.  The  contractor  will  be  held  strictly  accountable  for  any 
variation  or  difference  between  the  grades  of  reset  manholes  and 
boxes  and  that  of  the  contiguous  pavement,  and  any  such  differ- 
ence existing  on  the  completion  of  the  work,  or  occurring  during 
the  maintenance  period  thereof,  shall  be  corrected  by  the  con- 
tractor at  his  own  expense. 

13.  MATERIALS   TO   BE   REMOVED. — BLOCKS   AND   BRIDGE- 
STONES  TO  BE  LOADED. — OLD  CURBSTONES.     All  old  materials 
necessary  to  be  removed  in  the  preparation  for  paving,  excepting 
manhole  heads  and  boxes  and  the  materials  herein  mentioned, 
shall  be  the  property  of  the  contractor,  and  shall  be  immediately 
removed  by  him  off  t ha  line  of  the  work.     Paving  blocks  that  are 
to  be  used  again  shall  be  neatly  piled,  as  hereinafter  set  forth, 
and  such  as  are  not  so  required,  and  all  removed  bridgestones, 
shall  be  loaded  by  the  contractor  into  the  carts  or  wagons  of  the 
Bureau  of  Highways  and  shall  remain  the  property  of  the  City. 
Old  curbstones  which  cannot  be  utilized  in  accordance  with  the 
terms  of  these  specifications  shall  become  the  property  of  the  con- 
tractor, to  be  disposed  of  by  him. 

14.  MATERIAL  TO  BE  USED  AGAIN. — PRICE  FOR  PAVEMENT  TO 
INCLUDE  REMOVAL. — Such  other  material  which  is  specially  suit- 
able for  use  in  the  work  shall  be  collected,  piled,  and  utilized  as 
directed  by  the  engineer.     All  the  work  of  removing  and  loading 
old  material,as  above,  shall  be  included  in  the  price  bid  per  square 
yard  of  pavement. 

15.  EXCAVATION    AND    FOUNDATION. — The    pavement    and 
other  materials  necessary  to  be  removed  shall  be  taken  up  and 
disposed  of,  as  required,  and  the  roadways  excavated  of  all  sub- 

17 


258  HIGHWAY   ENGINEERING 

soil  or  other  matter,  be  it  earth,  rock,  or  other  material,  to  a  uni- 
form subgrade  seven  and  one-half  (7J)  inches  below  the  top  of  the 
finished  pavement,  or  to  such  other  depth  as  the  engineer  may 
require.  No  ploughing  will  be  allowed  within  six  (6)  inches  of 
such  subgrade,  except  by  permission  of  the  engineer. 

16.  SPONGY  MATERIAL. — All  spongy  or  objectionable  matter 
disclosed  by  the  excavations  thus  made  shall  be  removed,  and  the 
space  filled  with  acceptable  material,  compacted  by  thorough 
ramming. 

17.  ROLLING. — UNSATISFACTORY  MATERIAL  TO  BE  REMOVED. 
— When  required,  the  entire  roadbed,  after  having  been  brought 
to  the  necessary  subgrade,  shall  be  rolled  with  a  steam  roller 
until  the  surface  is  thoroughly  compacted  and  the  inaccessible 
portions  shall  be  tamped,  wetted,  and  tamped  or  rolled  with  a 
small  roller  and  wetted,  as  may  be  directed.     Material  not  ad- 
mitting of  satisfactory  rolling  shall  be  removed,  and  such  new 
material  as  may  be  necessary  to  replace  the  same  or  bring  the 
pavement  to  the  proper  grade  shall  be  supplied  and  placed  by 
the  contractor  without  extra  compensation  therefor.     It  shall 
be  good,  wholesome  earth,  free  from  foreign  matter,  and  shall  be 
placed  in  layers  not  more  than  six  (6)  inches  in  depth  and  rolled 
or  rammed  as  above  or  as  may  be  directed. 

18.  ROADBED  SHAPING. — Great  care  shall  be  exercised  in 
shaping  the  roadbed  to  secure  a  uniform  surface  parallel  to,  and 
the  required  depth  below,  the  given  grade  and  crown,  and  the 
entire  cost  of  such  excavation  and  shaping  shall  be  included  in 
the  price  paid  for  pavement. 

19.  SAND  BED. — On  the  roadbed  thus  prepared  shall  be  laid 
a  concrete  foundation  of  the  materials  and  thickness  set  forth  in 
these  specifications,  and  thereon  shall  be  spread  a  layer  of  ce- 
ment mortar  to  such  a  depth  (in  no  case  less  than  one-half  [J]  an 
inch)  as  may  be  necessary  to  bring  the  surface  of  the  pavement  to 
the  proper  grade. 

20.  DELIVERY  OF  MATERIAL  AND  INSPECTION. — The  materials 


ASPHALT   PAVEMENTS  259 

for  construction  shall  not  be  brought  to  or  deposited  on  the 
street  in  quantities  greater  than  is  necessary  for  convenient  work- 
ing, and  shall  be  so  deposited  as  to  cause  the  least  possible  ob- 
struction to  streets  and  sidewalks,  as  may  be  determined  by  the 
engineer.  All  new  material  of  every  description  shall  be  care- 
fully inspected  after  it  is  brought  on  the  streets,  and  all  such  not 
conforming  in  quality  and  dimensions  to  these  specifications  will 
be  rejected  and  must  be  immediately  removed  from  off  the  line  of 
the  work. 

21.  ASSISTANCE  TO  BE  FURNISHED.     The  contractor  shall 
furnish  such  laborers  as  may  be  necessary  to  aid  the  engineer  in 
such  examinations,  and  in  case  he  shall  neglect  or  refuse  so  to  do, 
such  laborers  as  may  be  necessary  will  be  employed  by  the 
president  and  the  expense  therefor  will  be  deducted  from  and 
paid  out  of  any  money  then  due  or  which  may  thereafter  become 
due  to  the  said  contractor  under  this  agreement. 

22.  PILING  OF  MATERIAL. — All  old  and  such  new  material  as 
has  been  approved,  except  sand  and  broken  stone,  shall  be  neatly 
piled  by  the  contractor  on  the  front  half  of  the  sidewalk,  on 
planks  not  less  than  one  (1)  inch  thick  if  the  same  be  flagged  or 
otherwise  improved,  not  within  ten  (10)  feet  of  any  fire  hydrant 
and  with  sufficient  passageways  to  permit  of  free  access  from  the 
roadway  to  each  and  every  house  on  the  line  of  the  work. 

23.  Not  until  this  has  been  done  and  the  rejected  materials  re- 
moved entirely  from  the  line  of  the  work,each  of  which  conditions 
must  be  faithfully  fulfilled,  will  the  contractor  be  permitted  to 
proceed  with  the  laying  of  the  pavement. 

24.  OLD  CURBSTONES  THAT  MAY  BE  RESET. — Old  curbstones 
which  can  be  redressed  to  a  top  width  of  not  less  than  four  and 
one-half  (4J)  inches,  are  not  less  than  sixteen  (16)  inches  deep, 
and  are  of  the  quality  hereafter  specified,  shall  be  redressed,  re- 
jointed,  and  reset  as  directed  below.     All  friable  granite  curb- 
stones shall  be  rejected. 

25.  QUALITY, DIMENSIONS,  AND  DRESSING  OF  NEW  CURBSTONE. 


260  HIGHWAY   ENGINEERING 

—New  curbstones  shall  be  hard,  sound,  fine-grained,  and  uniform 
colored  bluestone,  shall  be  free  from  seams  and  other  imper- 
fections, and  shall  be  equal  in  quality  to  the  best  North-River 

bluestone.     They  shall  be inches  in  depth,  from  three  and 

one-half  (3J)  to  eight  (8)  feet  in  length,  and  not  less  than  five  (5) 
inches  in  thickness  (except  as  noted  for  bottom  of  curb),  with 
square  ends  of  the  full  average  width.  The  face  for  a  depth  of 
....  inches  and  the  top,  on  a  bevel  of  one-half  (J)  an  inch  in 
its  width  of  five  (5)  inches,  shall  be  dressed  to  a  surface,  which 
shall  be  out  of  wind  and  shall  have  no  depressions  measuring 
more  than  one-quarter  (|)  of  an  inch  from  a  line  or  straight  edge 
of  the  same  length  as  the  curbstone.  The  remainder  of  the  face 
shall  be  free  from  projections  of  more  than  one-half  (J)  an  inch, 
and  the  back  for  three  (3)  inches  down  from  the  top  shall  have  no 
projections  greater  than  one-quarter  (J)  of  an  inch  measured  from 
a  plane  at  right  angles  to  the  top.  The  bottom  of  the  curb  shall 
be  rough-squared  with  a  width  of  not  less  than  three  (3)  inches. 

The  sample  of  the  curbstones  showing  the  dressing  and  the 
jointing  required  can  be  seen  at  the  office  of  the  chief  engineer 
of  the  Bureau  of  Highways. 

26.  JOINTING. — For  the  full  width  of  the  stone  for  a  distance 
down  the  same  as  the  above-mentioned  depth  of  dressed  face 
from  the  top,and  there  below  to  the  bottom  fora  width  of  two  (2) 
inches  back  from  the  face,  the  ends  shall  be  squarely  and  evenly 
jointed.     In  no  case  shall  the  ends  of  the  curbstones  abutting 
basin-heads  be  bevelled  off  or  reduced  in  width,  but  recesses 
shall  be  neatly  cut  in  such  basin-heads  without  charge  therefor, 
to  give  square,  close  joints  or  the  full  width  of  the  stones. 

27.  SETTING. — Each  curbstone  shall  be  set  truly  to  grade  and 
line  and  on  a  face  batter  of  one  (1)  inch  in  its  depth,  or  vertically 
as  shall  be  directed;  it  shall  be  firmly  bedded  and  tamped,  and 
the  rear  to  the  top  back  filled  and  tamped,  with  clean,  dry,  gritty 
earth  or  coarse  sand,  free  from  rock  fragments,  or  as  hereinafter 
more  particularly  set  forth,  and  the  vertical  face  joints  of  all 


ASPHALT    PAVEMENTS  261 

curbstones  shall  be  flush  pointed  firmly  with  good  mortar  of  one 
part  of  Portland  cement  and  two  of  sand  from  the  top  of  the  curb 
to  the  top  of  the  foundation  of  the  asphalt-block  pavement. 

28.  CORNER  CURBSTONES. — Curved  curb  for  corners  shall  be 
cut  with  true  radial  joints  and  set  accurately  to  a  radius  of  six  (6) 
feet  in  three  (3)  foot  lengths,  unless  otherwise  required.     It  shall 
be  paid  for  as  straight  curb,  and  must  comply  in  all  respects  with 
the  above  requirements  therefor. 

29.  The  cost  of  excavation  necessary  for  curb-setting  shall  be 
included  in  the  price  paid  per  linear  foot  of  curb,  and  no  com- 
pensation therebeyond  shall  be  made  or  allowed. 

30.  CURB  ON  CONCRETE. — When  specified,    the    curbstone 
aforesaid  shall  be  set  on  a  concrete  foundation  and  the  price  sub- 
mitted per  linear  foot  for  new  curbstone  shall  include  the  fur- 
nishing of  the  stone  and  all  the  excavations  necessary  for  the 
concrete  foundation. 

31.  CONCRETE  BED  FOR  CURBSTONE. — The  concrete  founda- 
tion for  curbstone  shall  not  be  less  than  six  (6)  inches  thick  and 
eighteen  (18)  inches  in  width  and  be  of  the  materials  and  pro- 
portions hereinafter  described  except  that  the  broken  stone  shall 
not  be  less  than  one-quarter  (J)  nor  more  than  one  and  one-half 
(1J)  inch  maximum  dimensions;    the  curb  to  be  immediately 
bedded  on  the  centre  thereof,  with  a  bearing  for  its  full  length 
as  soon  as  the  concrete  is  laid,  and  it  shall  be  at  once  backed 
up  with  concrete  for  a  width  of  six  (6)  inches,  extending  from 
the  bottom  bed  to  within  four  (4)  inches  of  the  top  of  the  stone. 
The  concrete  so  used  will  be  paid  for  at  the  general  price  bid  per 
cubic  yard  for  concrete. 

32.  FRONT  CONCRETE.— Simultaneously  with  the  backing  up 
in  the  rear,  the  concrete  in  front  of  the  curb  shall  be  carried  up, 
for  the  exposed  width  of  the  bottom  bed,  to  the  elevation  of 
the  bottom  of  the  paving  foundation,  and  so  much  of  said  paving 
foundation  itself  as  may  be  necessary,  for  a  width  not  less  than 
six  (6)  inches  from  the  curb,  shall  be  immediately  laid  to  serve  as 


262  HIGHWAY   ENGINEERING 

a  support  for  the  curbstones.  When  set  the  corners  of  the  curb 
at  the  top  shall  be  a  straight  and  true  line,  and  the  upper  and  face 
surfaces  a  plane  surface. 

33.  IN  FRONT  OF  CONCRETE  WALKS. — When  curb  is  set  in 
front  of  a  monolithic,  cement,  or  concrete  sidewalk,  the  space  be- 
tween the  curb  and  sidewalk  foundation  shall  be  completely 
filled  with  concrete,  similar  to  that  on  which  curb  is  set,  to  within 
two  (2)  inches  of  the  top;  the  remaining  space  to  be  filled  with 
Portland  cement  of  the  quality  hereinafter  specified,  mixed  with 
equal  parts  of  crushed  stone  used  for  the  wearing  surface  of  such 
walks.     The  concrete  used  for  foundation  and  setting  curbstones 
will  be  paid  for  by  the  cubic  yard,  the  same  as  the  price  bid  for 
concrete,  and  the  dimensions  will  be  based  upon  these  herein- 
before stated. 

34.  REMOVAL  OF  FLAGSTONES. — MONOLITHIC  WALKS. — BACK- 
FILLING.— The  front  course  of  flagstones  when  not  over  four  (4) 
feet  in  width  interfering  with  the  work  of  curb-setting  shall  be 
picked  up  and  be  set  back,  and  after  the  curb  has  been  set  and 
thoroughly  backfilled  they  shall  be  fitted  in  their  original  posi- 
tion and  the  cut  edge  be  retrimmed  and  rejointed  to  a  true  line  to 
give  a  joint  when  possible,  not  more  than  one-half  (J)  an  inch 
wide  at  the  back  of  the  curb  and  be  so  relaid  to  the  new  curb  grade 
when  such  grade  does  not  differ  more  than  (5)  inches  from  that 
originally  existing;  the  stone  to  be  thoroughly  bedded  and  the 
joints  cemented  as  herein  set  forth.     Stone  of  unusual  size  and 
those  containing  coal-hole  openings,  ventilation,  or  light  castings 
shall  in  no  case  be  disturbed,  but  the  front  edge  shall  be  rejointed 
to  line,  as  above  in  place.     Monolithic  walks  shall  be  carefully 
cut  off  to  a  true  line,  five  and  one-half  (5J)  inches  back  of  and 
parallel  to  the  new  curb-line,  and  for  use  in  such  locations  curb- 
stones shall  be  selected  of  as  near  as  possible  a  uniform  width 
throughout  its  depth  that  the  foundation  of  the  walk  may  not  be 
unnecessarily  damaged.     The  entire  space  between  back  of  curb 
and  such  walks,  or  stones  that  are  left  in  place  (except  where 


ASPHALT   PAVEMENTS  263 

curbstones  are  to  be  set  in  concrete  as  above  described),  shall 
be  backfilled  with  fine  sand,  free  from  gravel  and  stones,  to  within 
two  (2)  inches  of  the  top  of  the  curbstones, water  being  freely  used 
to  settle  and  compact  the  same.  The  remaining  space  shall  be 
filled  with  Portland  cement  mixed  with  sand  or  stone  as  used  for 
such  walks,  to  be  neatly  trowelled  to  place,  and  the  contact  sur- 
faces of  stones  and  walks  shall  be  made  clean  and  wet  while  filling 
and  trowelling  the  said  two  (2)  inches. 

35.  Any   damage  done  by  the  contractor  to  sidewalks  in 
curb-setting,  handling,  or  in  the  storage  of  materials  shall  be 
made  good  by  him,  at  his  own  expense,  as  shall  be  directed  by 
the  engineer. 

36.  NEW  FLAGGING,  QUALITY  AND  DIMENSIONS. — DRESSING 
OF  FLAGSTONE. — New  flagging  furnished  to  replace  any  broken 
shall  be  of  bluestone  of  even  color  and  best  quality,  and  satis- 
factory to  the  president,  not  less  than  three  (3)  inches  thick,  even 
on  its  face,  free  from  seams,  flaws,  drill-holes,  or  discoloration, 
measuring  not  less  than  four  (4)  feet  wide,  and  containing  not 
less  than  twelve  (12)  superficial  feet  or  of  the  same  size  as  that 
broken,  as  shall  be  directed;    the  stones  to  be  chisel-dressed, 
with  sides  parallel,  on  the  four  edges  a  distance  down  of  one  (1) 
inch  from  the  top  and  at  right  angles  thereto;   except  that,  in 
sidewalks  where  stones  of  superior  dimensions  or  quality  are 
broken,  the  replaced  stone  must  be  in  length  and  width  not  less 
than  the  old  stone  and  be  of  the  same  quality  of  material. 

37.  LAYING  OF  FLAGSTONE. — CLEARING  UP. — All  flagging  to 
be  relaid  shall  be  firmly  and  evenly  bedded  to  the  grade  and  pitch 
required,  on  four  (4)  inches  of  steam  ashes,  clean,  gritty  earth  or 
sand,  free  from  clay  or  loam,  and  the  work  brought  to  an  even 
surface,  with  all  joints  close  and  thoroughly  filled  (except  around 
monuments  and  trees),  for  the  full  depth  with  cement  mortar, 
composed  of  equal  parts  of  the  best  Portland  cement  and  clean 
sharp  sand,  and  left  clean  on  the  surface,  and  all  earth,  debris,  and 
surplus  material  shall  be  removed  from  each  block  and  the  side- 


264  HIGHWAY   ENGINEERING 

walks  swept  clean  as  soon  as  the  work  thereon  has  been  com- 
pleted. 

38.  HEADING  STONES. — Wherever  the  new  pavement  abuts 
pavement  of  a  different  character,  and  wherever  directed  to  do 
so,  the  contractor  shall  put  down  bluestone  heading  stones  at 
least  three  (3)  feet  long  and  one  (1)  foot  deep  and  set  with  full 
bearing  on  a  bed  of  concrete  nine  (9)  inches  wide  and  six  (6) 
inches  deep,  of  the  quality  hereinafter  described.     These  head- 
ing stones  shall  be  of  good,  sound  bluestone,  free  from  lamination 
or  seams.     They  shall  be  dressed  square  on  top  to  a  good  sur- 
face, free  from  irregularities,  and  to  a  uniform  width  of  not  less 
than  four  and  one-half  (4J)  inches.     The  ends  shall  be  joined 
square  down  to  give  close  joints;and  the  bottoms  shall  be  nowhere 
less  than  three  (3)  inches  wide  and  be  cut  to  give  a  full,  square 
bearing  throughout,  and  the  sides  shall  be  free  from  bunches. 
These  stones  shall  be  maintained  by  the  contractor,  and  they  will 
be  paid  for  as  asphalt-block  surface. 

39.  SIZE  OF  BLOCKS. — PROPORTIONS  OF  MATERIALS. — The 
sizes  of  the  blocks  used  must  be  five  (5)  inches  wide,  three  (3) 
inches  deep,  and  twelve  (12)  inches  long,  and  a  variation  of  one- 
quarter  (J)  of  an  inch  from  these  dimensions  will  be  sufficient 
ground  for  rejecting  any  block.     The  blocks  must  be  composed  of 
crushed  trap  rock,  pulverized  carbonate  of  lime,  and  asphaltic 
cement,  mixed  in  the  following  proportions,  by  weight,  and  no 
change  from  such  proportions  shall  be  made  without  the  permis- 
sion of  the  engineer: 

Asphaltic  cement  6  to  11  parts 

Crushed  trap  rock 89  to  74  parts 

Pulverized  carbonate  of  lime .     5  to  15  parts 

40.  ASPHALTIC  CEMENT. — The  asphaltic  cement  shall  be  com- 
posed of  refined  asphalt  and  a  liquid  asphalt  or  other  suitable  flux. 
The  refined  asphalt  and  flux  shall  be  mixed  in  such  proportion  as 
will  produce  an  asphaltic  cement  of  a  consistency  and  quality 
as  approved  by  the  engineer. 


ASPHALT   PAVEMENTS  265 

The  refined  asphalt  shall  be  obtained  by  refining  crude  natural 
asphalt  until  the  product  is  homogeneous  and  free  from  water. 
Asphalt  obtained  from  the  distillation  of  asphaltic  oils  will  not 
be  accepted.  It  must  not  be  affected  by  the  action  of  the  water; 
must  contain  not  less  than  ninety  (90)  per  cent  of  bitumen 
soluble  in  carbon  bisulphide,  and  of  the  bitumen  thus  soluble  in 
carbon  bisulphide  not  less  than  sixty-eight  (68)  per  cent  shall  be 
soluble  in  boiling  Pennsylvania  petroleum  naphtha  (boiling- 
point  from  40  to  60  centigrade) ;  or,  if  it  does  not  contain  sixty- 
eight  (68)  per  cent  thus  soluble  in  naphtha,  but  is  satisfactory 
in  other  respects,  the  deficiency  may  be  supplied  by  fluxing  the 
refined  asphalt  with  such  a  percentage  of  a  viscous  liquid  as- 
phalt, satisfactory  to  the  engineer,  as  will  bring  it  up  to  the  re- 
quired standard.  The  refined  asphalt,  the  asphaltic  cement,  and 
the  flux  must  each  comply  in  all  respects  with  the  following  tests : 

(a)  Flash  test  not  less  than  300°  Fahrenheit.  (The  flash  test 
shall  be  taken  in  a  New  York  State  closed  oil-tester.) 

(6)  Fire  test  not  less  than  350°  Fahrenheit. 

(c)  No  appreciable  amount  of  light  oils  or  matter  volatile 
under  250°  Fahrenheit. 

(d)  Matter  volatile  at  350°  Fahrenheit  in  24  hours,  less  than  8 
per  cent.     (The  test  for  "  matter  volatile  at  350°  Fahrenheit  " 
shall  be  made  with  approximately  50  gms.  of  oil,  in  an  open,  flat- 
bottom,  cylindrical  dish  2£  ins.  hi  diameter  and  If  ins.  high. 
The  thermometer  shall  be  applied  so  as  to  register  the  tempera- 
ture of  the  oil.) 

(e)  It  shall  be  free  from  coke  and  any  manner  or  form  of 
adulteration. 

41.  TESTING  OF  BLOCKS. — The  blocks  furnished  will  be  sub- 
ject to  the  approval  of  the  engineer,and  shall  withstand  such  tests 
for  specific  gravity,  abrasion,  tensile  and  crushing  strength  as  he 
may  prescribe.  Whatever  the  character  of  the  asphalt  used,  the 
block  shall  yield,  when  extracted  with  bisulphide  of  carbon  and 
after  the  evaporation  of  the  solvent,  not  less  than  five  and  one- 


UNIYERSITY  OF  CALIFORNIA 

DEPARTMENT  OF  CIVIL  ENGINEERING 

BERKELEY.  CALIFORNIA 


266  HIGHWAY    ENGINEERING 

half  (5J)  nor  more  than  seven  and  one-half  (7J)  per  cent  of  bitu- 
minous matter,  except  when  other  percentages  are  specially  per- 
mitted by  the  engineer. 

The  trap  rock  used  in  making  the  biocKS  must  be  entirely 
free  from  dirt  and  other  impurities,  and  must  be  crushed  so  that 
every  particle  will  pass  a  screen  having  holes  one-quarter  (i)  inch 
in  diameter.  The  blocks  must  receive  a  compression  in  the 
moulds  of  not  less  than  one  hundred  and  twenty  (120)  tons  upon 
each  block;  and  must  weigh  not  less  than  fifteen  and  one-half 
(15J)  pounds  per  block. 

42.  The  engineer  shall  further  have  the  right  to  make  tests 
and  examinations  at  the  contractor's  works  of  the  materials  pro- 
posed to  be  used,  and  to  reject  any  or  all  such  materials  as  he 
may  consider  not  to  be  in  compliance  with  these  specifications. 

43.  INSPECTION. — The  blocks  will  be  carefully  inspected  after 
they  are  brought  on  the  line  of  work,  and  all  blocks  which  in 
quality  and  dimensions  do  not  conform  strictly  to  the  require- 
ments will  be  rejected  and  must  be  immediately  removed  from 
the  line  of  work. 

44.  CEMENT. — The  cement  shall  be  of  the  best  quality  of 
American  Portland,  samples  of  which  must  be  submitted  at 
least  ten  (10)  days  (holidays  and  Sundays  excluded)  before  using, 
for  the  inspection  and  approval  of  the  chief  engineer,  and  no 
change  from  such  approved  brand  shall  thereafter  be  made  with- 
out the  submission  and  approval  of  samples.     It  will  be  required 
'that  the  various  deliveries  shown  by  samples  taken  from  the 
work  during  its  continuance  shall  exhibit  qualities  equal  or 
superior  to  those  developed  by  the  samples  submitted  as  afore- 
said. 

45.  QUALITY. — TENSILE  STRENGTH. — All  cements  shall  be 
freshly  ground  and  of  a  uniform  quality,  color,  and  weight,  and 
briquettes  of  one  (1)  square  inch  section  shall  develop  or  exceed 
the  following  tensile  strength : 

Neat,  one  hour  air,  twenty-three  (23)  hours  in  water,  200  Ibs.; 


ASPHALT   PAVEMENTS  267 

neat,  one  day  air,  six  (6)  days  in  water,  400  Ibs. ;  neat,  one  day 
air,  twenty-seven  (27)  days  in  water,  480  Ibs. ;  one  of  Portland, 
three  (3)  of  sand,  one  day  air,  six  (6)  days  water,  150  Ibs. 

46.  CONCRETE,  PROPORTIONS  OF  MATERIALS. — THE  UNIT  OF 
MEASURE. — The  concrete  shall  be  composed  of  one  (1)  part  of 
cement,  three  (3)  parts  of  sand,  and  six  (6)  parts  of  broken  stone, 
but  should  the  proportion  of  voids  in  the  stone  be  such  that  a 
greater  or  less  quantity  of  stone  be  required  to  give  satisfactory 
results,  the  amount  of  broken  stone  shall  be  increased  or  de- 
creased to  the  extent  directed  by  the  engineer  upon  any  particu- 
lar piece  of  work.    The  unit  of  measure  shall  be  the  barrel  of  ce- 
ment as  packed  by  and  received  from  the  manufacturer. 

47.  SAND  AND  BROKEN  STONE. — To  BE  STORED  ON  PLATFORM. 
— The  sand  shall  be  clean,  coarse,  and  sharp,  and  be  free  from 
loam  or  dirt.     The  broken  stone  shall  be  of  trap,  granite,  or  lime- 
stone, or  such  other  stone  taken  from  line  of  the  work  as  shall 
be  satisfactory  in  the  judgment  of  the  engineer.     It  shall  be  en- 
tirely free  from  dust  and  dirt  and  be  of  graded  sizes  that  will  pass 
in  any  direction  through  a  revolving  circular  screen  having  holes 
two  and  one-half  (2})  inches  in  diameter,  and  be  retained  by  a 
screen  having  holes  one  (1)  inch  in  diameter.     The  sand  and 
stone  must  be  placed  upon  board  platforms  and  kept  free  from 
dirt,  and  the  cement  shall  be  properly  blocked  up  and  pro- 
tected from  dampness. 

48.  SIZE  OF  BATCH. — MIXING. — USE  OF  MIXING  MACHINE. — 
Concrete,  unless  machinery  be  used,  shall  be  mixed  in  batches, 
containing  not  more  than  one  (1)  barrel  of  cement  with  the  req- 
uisite proportion  of  other  material,  on  suitable  tight  platforms, 
not  less  than  twelve  (12)  feet  by  twelve  (12)  feet  in  size.     The  ce- 
ment and  sand  shall  be  thoroughly  mixed  dry  after  which  the 
broken  stone,  having  first  been  wetted,  shall  be  added.     The 
whole  mass  shall  then  be  turned  and  worked  by  skilled  laborers, 
until  a  resultant  is  obtained,  with  the  stone  uniformly  distributed. 
In  shovelling,  the  material  must  be  lifted  clear  of  the  board.     If 


268  HIGHWAY   ENGINEERING 

a  concrete  mixing  machine  be  used,  the  cement  and  sand  shall 
be  mixed  as  above  and  precautions  taken  to  insure  the  proper 
proportion  of  each  of  the  materials,  so  that  the  resultant  mixture 
shall  be  uniform  in  quality. 

49.  LAYING. — CONCRETE  SURFACE  TO  BE  SCABBLED. — The 
concrete  shall  be  placed  in  position  and  there  rammed  with 
proper  rammers  until  thoroughly  compacted.     The  whole  opera- 
tion of  mixing  and  laying  each  batch  must  be  performed  as  ex- 
peditiously  as  possible,  and  in  no  case  shall  concrete  be  used  which 
has  been  mixed  more  than  one-quarter  (J)  of  an  hour.     The 
concrete  shall  be  protected  from  the  weather  until  set,  and  should 
it  at  any  time  be  considered  by  the  engineer  to  be  poorly  mixed  or 
not  to  be  setting  properly,  such  portions  shall  be  taken  up  and 
replaced  with  satisfactory  material.     Sufficient  time,  of  which 
the  engineer  shall  be  the  judge,  shall  be  allowed  for  the  concrete 
to  set  before  the  pavement  is  laid  thereon.     Before  laying  con- 
crete to  connect  with,  rest  upon,  or  overlap  any  concrete  previous- 
ly laid,  the  entire  surface  of  contact  of  the  latter  shall  be  swept 
and  washed  clean  of  all  dirt  and  mortar  particles  and,  when 
deemed  necessary,  shall  be  satisfactorily  scabbled. 

50.  No  TRAFFIC  ON  CONCRETE. — No  horses,  carting,  or  wheel- 
ing shall  be  allowed  on  the  concrete  until  the  same  has  thoroughly 
set,  and  then  only  on  planks  furnished  and  laid  by  the  contractor. 
By  car  tracks  the  contractor  shall  provide  men  to  pass  cars  there- 
over. 

51.  THICKNESS  AND  TESTING. — The  concrete  foundation  shall 
be  four  and  one-half  (4£)  inches  thick,  including  a  mortar  top 
surface  of  one-half  ( J)  inch  in  thickness,  the  concrete  proper  being 
four  (4)  inches  thick  and  shall  withstand  such  tests  as  the  engi- 
neer may  deem  necessary,  and  the  contractor  shall  furnish  such 
samples  as  may  be  required  for  the  purpose. 

52.  On  the  concrete  surface,  after  the  same  has  been  swept 
and  made  wet,  shall  be  spread  a  layer  of  cement  mortar  to  such 
thickness  that  when  struck  to  a  surface  three  (3)  inches  below  and 


ASPHALT   PAVEMENTS  269 

exactly  parallel  to  the  grade  of  the  completed  pavement  its  depth 
shall  be  nowhere  less  than  one-half  (J)  an  inch.  The  mortar 
shall  consist  of  one  (1)  part  of  slow-setting  Portland  cement,  of  an 
approved  quality,  mixed  with  four  (4)  parts  of  clean,  sharp  sand, 
free  from  gravel,  over  one-quarter  ( J)  of  an  inch  in  diameter,  and 
it  shall  be  spread  and  surfaced  as  follows : 

53.  On  the  surface  of  the  concrete  shall  be  set  strips  of  wood 
four  (4)  inches  wide  by  one-quarter  (J)  inch  thick,  or  strips  of 
steel  four  (4)  inches  wide  by  not  less  than  one-eighth  (£)  inch 
thick,  and  of  the  greatest  length  convenient  for  handling.    These 
strips  shall  be  carefully  set  parallel  and  about  eight  (8)  or  ten. 
( 10)  feet  apart,  running  from  curb  to  curb,  and  be  embedded  in 
mortar  throughout  their  length  so  that  the  top  surface  shall  be 
three  inches  below  and  parallel  to  the  grade  of  the  finished  pave- 
ment.    The  space  between  two  strips  having  been  filled  with 
mortar,  a  true  and  even  top  surface  shall  be  struck  by  using  an 
ironshod  straight  edge  on  the  strips  as  a  guide,  and  as  soon  as  the 
bed  has  been  struck  the  strip  which  would  interfere  with  laying 
the  block  shalJ  be  removed  and  its  place  carefully  filled  with  mor- 
tar with  a  trowel. 

54.  If  the  width  of  the  roadway  be  such  that  the  laying  of 
blocks  on  a  complete  section  cannot  be  completed  before  the 
mortar  takes  its  initial  set,  the  strips  may  be  placed  parallel 
to  the  curb,  and  templates  cut  to  the  curve  of  the  desired  crown 
shall  be  used  on  these  strips  to  strike  the  bed. 

55.  SAND  BED. — On  this  mortar  surface,  spread  and  smoothed 
as  above  to  the  proper  crown  and  grade,  the  blocks  are  to  be  laid 
with  close  joints  and  uniform  top  surface,  in  courses  at  right 
angles  to  the  line  of  the  street,  except  in  and  between  car  tracks, 
in  intersections,  and  hi  other  special  cases,  when  they  shall  be 
laid  diagonally,  as  shall  be  directed. 

56.  CUTTING  CLOSURES. — Nothing  but  whole  blocks  shall  be 
used  except  in  starting  a  course  or  hi  such  other  cases  as  shall  be 
specially  permitted  by  the  engineer,  and  in  no  case  shall  less  than 


270  HIGHWAY   ENGINEERING 

one-third  of  a  block  be  used  in  breaking  joints.  Closures  shall 
be  carefully  cut  and  trimmed  by  experienced  men,  the  portion  of 
the  block  to  be  used  to  be  free  from  check  or  fracture  and  the 
cut  end  to  have  a  surface  normal  to  the  top  of  the  block  and  be 
cut  at  the  proper  angle  to  give  a  close,  tight  joint. 

57.  LAYING. — Each  course  of  blocks  shall  be  of  uniform  width 
and  depth,  with  all  joints  close  and  the  end  joints  broken  by  a 
lap  of  at  least  four  (4)  inches,  and,  while  laying,  the  pavers  must 
stand  on  those  already  laid.     Any  lack  of  uniformity  in  the  sur- 
face or  unevenness  in  the  blocks  must  be  immediately  corrected 
by  taking  up  and  relaying  the  blocks,  and  blocks  fractured  or 
broken  shall  be  replaced  with  perfect  ones  before  any  sand  is 
spread  over  the  surface. 

58.  SAND  JOINTS  AND  COVERING. — When  laid,  the  blocks  shall 
be  covered  with  clean,  fine  sand,  entirely  free  from  loam  or  earthy 
matter,  perfectly  dry  and  screened  through  a  sieve  having  not 
less  than  twenty  (20)  meshes  per  linear  inch,  the  sand  to  be  swept 
and  brushed  into  the  joints  and  left  on  the  surface  until  such 
time  when,  if  required  by  the  engineer,  the  pavement  shall  be 
swept  clean  for  final  inspection  and  any  defects  then  noted  shall 
be  remedied. 

59.  READJUSTING  OF  ADJOINING  PAVEMENT. — The  curbstones 
and  gutters  of  the  adjoining  pavements,  and  all  pavements  abut- 
ting the  new  work,  shall  be  readjusted  and  brought  to  the  new 
grades  and  lines  to  the  extent  deemed  necessary  by  the  engineer, 
and  such  readjustment   of  curb   and  pavement  shall  include 
rejoin  ting,  resetting,  and  relaying  as  herein  provided,  all  without 
charge  therefor. 

60.  In  readjusting  such  abutting  pavements,  all  imperfect 
stones  shall  be  discarded  and  only  those  of  regular  shape  used, 
and  before  the  old  pavement  of  the  street  being  paved  shall  have 
been  removed  the  contractor  shall  select  therefrom  enough  per- 
fect stones,  and  preserve  the  same  till  needed,  to  make  up  any 
deficiencies.    On  the  contractor's  failure  so  to  do,  he  shall  pro- 


ASPHALT   PAVEMENTS  271 

vide  such  extra  necessary  stones  at  his  own  expense  and  to  the 
satisfaction  of  the  engineer. 

61.  The  stones  shall  be  laid  in  straight  and  regular  courses, 
with  close  end  joints  broken  by  a  lap  of  at  least  three  inches. 
The  joints  between  courses  shall  be  close  except  when  gravel  fill- 
ing is  to  be  used,  and  the  courses  shall  be  carried  parallel  to  the 
existing  courses;    any  differences  in  alignment  between  such 
courses  and  the  header  shall  be  corrected  at  the  header  by  neatly 
trimming  the  blocks.    None  but  stones  of  the  same  width  shall 
be  used  in  the  same  course  except  where  trimming  is  necessary. 

62.  All  stones  shall  be  relaid  on  a  full  bed  of  sand  and  be 
thoroughly  rammed  to  a  firm  unyielding  bearing  and  to  a  uniform 
surface,  the  joints  to  be  brushed  full  of  sand. 

63.  When  the  pavement  is  to  be  relaid  on  a  concrete  founda- 
tion with  joint  filling,  such  foundation,  if  required  by  the  engi- 
neer, shall  be  removed  and  relaid,  or  be  added  to  with  concrete  as 
may  be  necessary;  all  other  detail  to  be  in  accordance  with  the 
current  specifications  for  similar  work  in  use  in  the  Bureau  of 
Highways. 

64.  REMOVAL  OF  SURPLUS  MATERIALS,  RUBBISH,  ETC. — All 
surplus  materials,  earth,  sand,  rubbish,  and  stones  are  to  be  re- 
moved from  the  line  of  the  work,  block  by  block,  as  rapidly  as 
the  work  progresses;  all  material  covering  the  pavement  and  side- 
walks shall  be  swept  into  heaps  and  immediately  removed  from 
the  line  of  the  work;  and  unless  this  be  done  by  the  contractor 
within  forty-eight  hours  after  being  notified  so  to  do,  by  a 
written  notice  to  be  served  upon  the  contractor,  either  personally 
or  by  leaving  it  at  his  residence  or  with  any  of  his  agents  on  the 
work,  to  the  satisfaction  of  the  president,  the  same  shall  be  re- 
moved by  the  said  president  and  the  amount  of  the  expense  there- 
of shall  be  deducted  out  of  any  moneys  due  or  to  grow  due  to  the 
contractor  under  this  agreement. 

65.  SWEEPING  AND  SPRINKLING. — At  all  times  during   the 
prosecution  of  the  work,  such  materials  as  may  be  placed  on  the 


272  HIGHWAY   ENGINEERING 

sidewalk  shall  be  piled  in  the  manner  heretofore  set  forth,  and 
the  contractor  shall  keep  the  footway  clean  by  sweeping.  When 
such  material  is  removed,  the  sidewalk  must  be  immediately 
swept  clean  by  the  contractor,  and  when  public  or  local  incon- 
venience is  caused  by  dust,  the  contractor  shall  water  any  piles 
or  surfaces  of  earth  or  the  sidewalks  or  pavement  foundation 
during  sweeping,  when  and  where  necessary  or  whenever  required 
by  the  engineer  so  to  do. 

66.  PATENTED  ARTICLES. — That  whenever  or  wherever  an 
article  or  any  class  of  materials  is  specified  by  the  name  of  any 
particular  patentee,  manufacturer,  or  dealer,  or  by  reference  to 
the  catalogue  of  any  such  manufacturer  or  dealer,  it  shall  be  taken 
as  intending  to  mean  and  specify  the  article  or  materials  de- 
scribed, or  any  other  equal  thereto  in  quality,  finish,  and  dura- 
bility, and  equally  as  serviceable  for  the  purposes  for  which  it  is 
(they  are)  intended.  Nothing  in  these  specifications  shall  be  in- 
terpreted or  taken  to  violate  the  provisions  of  section  1554  of  the 
Greater  New  York  Charter,  which  provides  that  "  except  for  re- 
pairs no  patented  pavement  shall  be  laid  and  no  patented  article 
shall  be  advertised  for,  contracted  for,  or  purchased,  except  under 
such  circumstances  that  there  can  be  a  fair  and  reasonable  op- 
portunity for  competition,  the  conditions  to  secure  which  shall  be 
prescribed  by  the  Board  of  Estimate  and  Apportionment." 


CHAPTER  X 

MODERN   WOODEN   PAVEMENTS 

DEFINITION.  Such  a  term  implies  one  in  which  the  surfacing 
material  consists  of  wooden  blocks,  of  approved  form,  which  may 
or  may  not  have  been  impregnated  with  some  preservative  to 
prevent  decay  and  expansion,  laid  upon  a  suitable  foundation. 

HISTORY.  Wooden  pavements  are  by  no  means  a  new  de- 
parture either  in  this  country  or  abroad,  for  in  Europe  they  have 
been  known  for  several  hundred  years,  having  been  first  laid  in 
Russia  in  the  form  of  hexagonal  blocks,  while  in  the  United 
States  they  have  been  employed  during  the  past  seventy  years, 
first  being  laid  in  New  York  City  about  1835. 

In  Europe  they  have  given  unquestionable  satisfaction,  so 
that  both  London  and  Paris  are  quite  predisposed  in  their  favor. 
The  former  city  began  the  use  of  wooden-block  pavements  about 
1839,  but  with  little  success  as  the  soft  wood,  inferior  quality  of 
the  same,  poor  foundation,  and  general  lack  of  knowledge 
regarding  construction  produced  a  covering  that  was  quickly 
disrupted. 

In  the  light  of  experience,  however,  and  with  the  use  of  hard 
woods  carefully  cut  and  laid  on  a  concrete  base,  better  results 
have  been  obtained.  That  such  pavements  may  be  satisfactorily 
employed  under  the  severest  conditions  of  traffic  is  instanced  in 
that  on  the  very  busiest  thoroughfares  of  both  London  and 
Paris,  such  as  the  Strand  and  the  Avenue  de  1'Opera,  wooden 
blocks  are  selected  in  preference  to  all  others. 

The  reason  for  the  marked  success  of  wooden  block  abroad,  as 
compared  with  the  lack  of  it  in  this  country,  is  that  there  very 
18  273 


274  HIGHWAY   ENGINEERING 

much  more  attention  is  given  to  the  selection  and  treatment  of 
the  material  used,  to  the  foundation,  to  the  joints,  and  to  the 
maintenance  of  the  pavement  after  it  is  laid.  Heretofore,  in 
the  United  States,  green  wood  has  been  frequently  used,  laid 
upon  an  improper  or  poorly  constructed  foundation,  with  a 
joint  filling,  failing  in  its  purpose  to  keep  out  the  moisture,  and 
with  too  little  or  no  regard  for  maintenance.  Besides  this,  the 
many  and  great  advantages  of  brick  pavements  have  tended  to 
reduce  the  demand  for  wooden  blocks.  The  present  practice, 
however,  indicates  that  better  results  are  being  obtained;  due, 
unquestionably,  to  a  marked  improvement  of  laying,  and  also  to 
an  increasing  regard  for  the  fundamental  principles  underlying 
maintenance. 

ADVANTAGES.  It  would  seem  from  a  careful  examination 
that  the  advantages  in  favor  of  wood  pavements  far  outweigh 
the  disadvantages.  The  former  may  be  stated  as  follows  : 

1.  Smooth. 

2.  Low  in  tractive  resistance,  requiring  much  less  effort  to 
haul  a  unit  load  than  over  a  granite-block  pavement,  and  only  a 
little  more  than  that  required  on  asphalt. 

3.  Noiseless,  so  that  wooden  block  has  been  popularly  termed 
"  the  silent  pavement."     In  this  respect  wood  is  superior  to 
asphalt  in  that  horses'  hoofs  do  not  resound  upon  it,  and  it  may 
be  said  to  have  "  the  effect  of  a  carpet  of  tan  bark  as  corn- 
pared  with  pavements  of  stone."     For  this  reason  it  is  particular- 
ly desirable  in  the  vicinity  of  hospitals,  schools,  churches,  and 
other  places  where  noise  may  not  be  tolerated. 

4.  It  affords  an  excellent  foothold  on  grades  less  than  about 
four  per  cent,  and  has  been  used  on  grades  greatly  in  excess  of 
this,  where  the  traffic  was  heavy.     It  is  true  that  under  certain 
weather  conditions  the  pavement  becomes  slippery,  but  hardly 
to  a  greater  degree  than  asphalt. 

5.  It  is  clean,  sanitary,  easily  cleaned,  creates  no  mud,  nor 
does  it  pulverize,  as  asphalt,  into  a  fine  dust. 


MODERN  WOODEN  PAVEMENTS  275 

6.  It  is  suited  to  all  kinds  of  traffic,  from  the  lightest  to  the 
heaviest. 

7.  It  is  durable,  lasting  longer  than  any  other  pavement  but 
granite  block.     For  example,  in  Boston,  such  a  pavement,  laid 
on  Tremont  Street,  where  the  traffic  is  heavy,  shows  after  seven 
years  of  continuous  service  a  compression  or  wear  of  the  blocks 
to  the  extent  of  only  three-sixteenths  inch.     Such  wear  is  due  to 
horses'  hoofs  as  much  as  to  the  action  of  wagon  wheels,  and  the 
former  increases  very  materially  with  increase  in  grade.     Wide 
joints  also  promote  wear,  as  then  the  fibres  of  the  blocks  more 
easily  spread  or  broom. 

8.  The  pavement  is  easily  maintained  and  presents  no  dif- 
ficulties, when  access  is  desired,  either  in  the  removal  of  the  blocks 
or  the  replacement  of  the  same. 

DISADVANTAGES.    The  principal  disadvantages  seem  to  be: 

1.  Cost;  this  factor  rising  to  $3.00  per  square  yard,  including 
the  concrete  foundation. 

2.  It  is  said  to  be  hard  to  clean  compared  with  asphalt. 

3.  In  wet  weather  it  is  slippery. 

These  statements  are  only  relative,  for  while  it  may  be  harder 
to  clean  a  wooden-block  pavement  than  asphalt,  on  the  other 
hand  it  is  very  much  less  difficult  than  granite  or  stone  block.  It 
may  be  said  also  that  though  wooden  block  becomes  slippery  dur- 
ing rainy  weather,  this  condition  may  be  counteracted  some- 
what by  the  application  of  sand  to  the  surface.  Objections,  too, 
have  been  raised  on  the  ground  that  it  is  unsanitary  as  the  wood 
is  porous  and  the  joints  not  always  watertight.  The  porosity 
permits  of  absorption,  while  the  joints  allow  the  moisture  to  sink 
beneath  the  surface,  there  to  deposit  as  a  thick  slimy  liquid  with 
a  strong  ammoniacal  odor,  which  is  both  annoying  and  unhealth- 
ful.  That  such  conditions  need  not  exist  is  proven  by  the  fact 
that  in  London  after  thirty  years'  experience  complaints  of  this 
nature  had  never  been  received. 

Within  the  past  few  years  the  popularity  of  wooden-block 


276  HIGHWAY   ENGINEERING 

pavements  has  greatly  increased  in  the  United  States  so  that  in 
1906  Indianapolis,  New  York,  Minneapolis,  Toledo,  and  Boston 
alone  had  over  1,400,000  square  yards  of  such  pavements  laid. 

WOOD  USED.  At  present  the  woods  most  commonly  used  in 
the  United  States  are  Long-leaf  Yellow  Pine,  Southern  Black 
Gum,  Norway  Pine,  Tamarac,  Washington  Fir,  and  Cedar. 

In  England,  however,  both  the  hard  and  soft  varieties  are 
employed,  the  former  including  principally  those  from  West 
Australia,  Jarrah  and  Karri,  and  the  latter,  Baltic  Redwood  and 
Yellow  Deal. 

The  choice  between  hard  and  soft  woods  depends  chiefly  upon 
the  local  conditions,  as  any  wood  which  is  sound,  well  seasoned, 
free  from  sap,  shakes,  and  knots,  close-grained,  and  uniform  in 
quality,  whether  hard  or  soft,  is  satisfactory. 

Hard  woods,  being  closer  grained,  absorb  less  moisture  and 
are  therefore  more  sanitary,  besides  which  they  wear  longer,  and 
are  usually  laid  without  being  treated  with  a  wood  preservative 
as  the  latter  can  enter  to  only  a  small  degree.  Very  hard  woods 
such  as  Oak  are,  however,  slippery,  do  not  give  as  good  a  foot- 
hold, and  do  not  wear  as  evenly. 

Soft  woods  are  laid  both  with  and  without  treatment,  but 
under  the  latter  circumstances  they  are  never  so  satisfactory  un- 
less the  extremely  rapid  wear  precludes  the  advisability  of  using 
a  preservative.  Without  impregnation,  soft-wood  blocks  absorb 
moisture,  are  unsanitary,  and  quickly  broom. 

DOUGLAS  FIR  OR  OREGON  PINE  is  the  most  satisfactory  wood 
that  may  be  selected  because  it  is  so  extremely  uniform  and 
homogeneous  in  character.  In  consequence  of  this  one  charac- 
teristic, it  wears  uniformly  and,  while  not  so  hard  and  tough  as 
Long-leaf  Yellow  Pine  or  Black  Gum,  gives  a  much  superior  pave- 
ment. It  is  not  so  well  suited  to  streets  where  the  very  heaviest 
traffic  is,  but  under  generally  normal  conditions  it  is  the  best  that 
may  be  employed.  East  of  the  Mississippi  River,  however,  its 
cost  is  prohibitive. 


MODERN  WOODEN  PAVEMENTS  277 

LONG-LEAF  YELLOW  PINE  is  the  wood  most  frequently  used, 
but  as  it  is  becoming  more  and  more  scarce  and  expensive,  sub- 
stitutes are  being  sought  for  hi  its  stead. 

SOUTHERN  BLACK  GUM  has  been  satisfactorily  employed  in 
Boston,  but  not  long  enough  to  definitely  determine  its  qualities. 
The  wood  in  itself  is  cheaper  than  Yellow  Pine,  and  there  is  less 
waste  to  it  hi  cutting,  shipping,  and  handling,  but  it  is  heavier, 
costing  more  for  transportation,  takes  longer  to  dry,  and  re- 
quires a  larger  quantity  of  preservative  per  cubic  foot  than  Yellow 
Pine. 

CEDAR  has  been  extensively  used  in  Chicago,  where  it  is  laid 
hi  the  form  of  round  blocks;  but  the  present-day  tendency  is  not 
toward  either  that  shape  or  sort  of  wood. 

NORWAY  PINE  and  TAMARAC  are  also  employed,  but  not  to 
the  same  extent  as  the  others. 

The  only  question  as  to  the  superiority  of  one  wood  over  an- 
other, provided  a  preservative  has  been  applied,  is  that  of 
durability.  "  The  probability  is  that  the  treated  woods  are 
equally  good  as  the  untreated  provided  the  traffic  does  not  pass 
the  limit  of  durability." 

"  It  would  seem  that  for  each  class  of  timber  there  is  a  con- 
dition of  traffic  beyond  which  it  should  not  be  subjected."  For 
the  heaviest  the  more  durable  woods  are  required,  such  as  long- 
leaf  yellow  pine  and  black  gum;  where  the  traffic  is  not  of  the 
heaviest,  woods  as  soft  as  Norway  Pine  may  be  used,  and  where 
it  is  light,  almost  any  wood  may  be  used  that  will  not  decay. 

FORMS  OF  BLOCK.  The  forms  of  block  used  are  numerous  and 
various,  differing  materially  both  in  shape  and  size.  The  shapes 
include  round,  square,  rectangular,  oblique,  hexagonal,  octago- 
nal, and  many  other  interlocking  forms,  but  present  tendencies 
favor  one  that  is  rectangular,  as  it  is  superior  in  many  ways. 
In  Europe  rectangular  blocks  are  used  almost  without  exception. 

The  dimensions  depend  upon  the  same  factors  that  govern 
the  size  of  granite  blocks,  and  are  usually  found  to  lie  between  the 


278  HIGHWAY    ENGINEERING 

following  values :  width,  3  to  4  ins. ;  depth,  4  to  6  ins. ;  length, 
9  to  12  ins.  The  width  is  influenced  by  the  size  of  a  horse's 
hoof,  the  depth  by  the  most  economical  value  that  may  be 
used  to  secure  a  maximum  amount  of  wear  before  renewal, 
leaving  a  minimum  thickness  to  be  discarded,  and  the  length 
upon  the  fact  that  blocks  too  long  split  readily. 

As  blocks  wear  down  2  or  3  ins.,  they  become  rough  and  must 
be  replaced  by  others,  in  consequence  of  which  a  thickness  of  6 
ins.  is  never  exceeded  and  seldom  reached,  as  it  involves  too 
great  a  waste  of  material. 

Uniformity  in  the  size  and  shape  of  the  block  is  essential  to 
insure  parallel  faces,  narrow  joints,  and  regularity  in  the  breaking 
of  joints;  to  secure  this,  the  wood  is  carefully  cut  by  machinery 
and  inspected  rigidly  to  eliminate  faulty  material. 

CHEMICAL   TREATMENT 

While  it  is  true  that  in  the  early  practice  untreated  blocks 
were  laid  only,  present  specifications  usually  require  that  the  wood 
shall  have  been  impregnated  with  some  preservative  fluid.  The 
purpose  of  this  is  that  the  pores  may  be  filled  by  the  liquid  or 
solution,  preventing  the  absorption  of  moisture  and  air  and  thus 
decay,  and  also  to  prevent  change  in  size. 

This  is  the  principal  difference  between  old  and  new  forms  of 
wooden  pavement. 

If  the  wood  is  prevented  from  decaying,  then  the  life  may  be 
said  to  depend  upon  the  durability  of  the  material  itself,  all  other 
things  being  equal. 

Many  methods  have  been  employed  for  the  preservation  of 
wood,  but  those  more  generally  used  are:  kyanizing,  using  a 
solution  of  corrosive  sublimate;  burnettizing,  in  which  zinc 
chloride  is  employed;  and  creosoting,  in  which  creosote  usually 
with  some  other  ingredient  is  impregnated.  The  two  latter 
are  the  ones  most  generally  used;  and  of  these,  creosoting  is 
the  best. 


MODERN   WOODEN   PAVEMENTS  279 


LAYING  THE   PAVEMENT 

FOUNDATION.  During  the  past,  various  foundations  have 
been  tried  in  the  United  States,  and  usually  with  not  too  satis- 
factory results.  This  may  be  partially  explained  by  the  fact 
that  in  early  days,  when  lumber  was  more  plentiful  and  cheaper, 
and  the  blocks  were  untreated,  the  pavement  was  not  always 
carefully  designed  and  laid,  nor  had  practice  developed  the 
standards  of  excellence  that  exist  to-day. 

Wooden  blocks  have  been  laid  directly  upon  the  natural  soil, 
on  one  or  two  layers  of  plank  resting  upon  the  ground  or  a  layer 
of  sand,  and  upon  a  concrete  base.  In  all  but  the  last  the  pave- 
ments wear  out  quickly,  and  far  from  demonstrate  the  possibili- 
ties that  exist  in  wood. 

It  is  claimed  that,  laid  upon  a  well-prepared  foundation  of  the 
natural  soil,  a  wooden-block  surfacing  is  cheap ;  but,  on  the  other 
hand,  its  life  is  short  as  the  blocks  quickly  decay  and  the  pave- 
ment soon  needs  mending. 

Where  planks  are  used  resting  upon  a  coat  of  sand,  it  is  cus- 
tomary to  place  1  to  2  in.  by  10  to  12  in.  stringers  longitudinally 
on  the  soil  along  the  street,  spaced  8  to  10  ft.  centre  to  centre,  and 
on  top  of  these,  transversely,  with  close  joints,  planks  of  ap- 
proximately the  same  dimensions.  The  ends  of  the  latter  rest 
upon  the  stringers,  and  are  supported  between  by  the  sand  in 
which  the  stringers  are  embedded.  Such  an  arrangement  dis- 
tributes the  pressure  and  gives  a  pavement  that  has  been  found 
to  be  satisfactory  in  Chicago,  where  they  are  extensively  used. 

Concrete  forms,  undoubtedly,  the  best  foundation  of  all.  It 
is  laid  to  a  depth  of  4  to  6  his.,  depending  upon  the  nature  of  the 
traffic  and  the  subsoil.  Over  the  concrete  is  placed  a  cushion 
coat  of  sand  J  to  1  in.  deep,  or  a  thin  layer  of  neat  cement  or  grout 
for  the  purpose  of  taking  up  all  irregularities  and  of  insuring  an 
even-bearing  surface  for  the  blocks. 

The  blocks  themselves  are  always  placed  with  the  fibre  verti- 


280  HIGHWAY    ENGINEERING 

cal  to  prevent  splitting,  and  with  the  long  edge  perpendicular  to 
the  axis  of  the  street. 

JOINTS  should  be  made  as  small  as  possible  since  wide  ones 
cause  the  fibres  to  spread.  This  applies  more  particularly  to 
streets  with  grades  less  than  3  per  cent,  as  above  that  open  joints, 
J  to  f  in.,  are  frequently  laid  to  afford  a  foothold.  When  the 
blocks  are  placed  close  together,  with  small  joints,  the  filling  used 
is  either  fine  hot  sand,  Portland-cement  grout,  or  hot  paving 
cement.  Sometimes  the  joint  filling  consists  of  a  bituminous  ce- 
ment for  a  depth  of  2  ins.,  while  on  top  of  this  is  placed  cement 
grout  in  the  proportions  of  1  of  cement  to  3  of  sand.  Where  soft 
woods  are  used,  the  surface  may  be  flushed  with  hot  tar  which  is 
brushed  into  the  joints,  while  with  hard  woods  one  end  and  one 
side  may  be  dipped  into  a  hot  paving-pitch  composition  with  the 
material  adhering,  forming  the  joints. 

Where  bitumen  is  used  in  close  joints,  it  allows  for  the  ex- 
pansion of  the  blocks,  permits  the  street  being  thrown  open  for 
traffic,  and  gives  a  more  even  surface,  because  it  prevents  the 
fibres  from  spreading. 

Portland-cement  joints,  on  the  other  hand,  require  a  space  of 
J  in.  between  blocks,  do  not  take  up  expansion,  make  the  pave- 
ment noisy,  develop  a  corduroy  effect,  and  under  heavy  loads  will 
split,  permitting  moisture  to  get  at  the  foundation,  besides  re- 
quiring from  5  to  10  days  to  set,  during  which  time  traffic  is  ex- 
cluded. Wide  joints  run  transversely  across  the  street  and  are 
filled  with  Portland  cement,  and  paving  cement  with  gravel  or 
sand. 

When  a  cement  grout  is  used,  the  £  to  |  in.  joints  are  secured 
by  laying  laths  1  in.  deep  and  of  required  thickness  on  the  foun- 
dation between  successive  rows  of  blocks  The  composition  of 
the  bitumen  used  in  joints  is  100  Ibs.  of  pitch  to  1J  gals,  of  oil. 

The  disadvantage  of  wide  joints  is  that  they  retain  the  dirt, 
increase  the  cost  of  cleaning,  and  are  noisy. 

EXPANSION  JOINTS.     To  prevent  heaving  and  to  allow  for  the 


MODERN  WOODEN  PAVEMENTS  281 

natural  change  in  volume  produced  in  either  soft  or  hard  woods, 
whether  treated  or  untreated,  when  exposed  to  the  varying  con- 
ditions of  atmosphere,  expansion  joints  are  left  next  each  curb 
as  in  asphalt-block  or  brick  pavements.  Such  joints  vary  in 
width,  depending  upon  the  nature  of  the  woods,  and  whether  the 
blocks  have  been  impregnated  or  not.  They  consist  of  a  layer  of 
sand  placed  between  the  blocks  and  the  curb  which  is  covered 
over  with  cement  grout  to  prevent  moisture  from  getting  at  the 
foundation.  When  the  blocks  have  expanded  as  much  as  they 
are  likely  to,  the  grout  and  sand  are  removed  and  the  space 
filled  with  cement  grout  or  other  material. 

Untreated  blocks  will  expand  at  the  rate  of  about  5  times  that 
of  treated  blocks,  so  that  if  in  a  pavement  30  ft.  wide,  2  ins.  at 
each  curb  should  be  left  for  expansion  with  treated  blocks,  and 
10  ins.  with  untreated  blocks.  Creosoting  tends  to  prevent  this 
expansion,  though  about  1  in.  for  every  8  ft.  in  width  is  allowed 
even  with  such  treatment. 

GRADE.  The  best  practice  would  seem  to  indicate  that,  as 
usually  laid,  a  grade  of  from  3  per  cent  to  4  per  cent  should  not  be 
exceeded,  though  blocks  have  been  used  in  London  on  grades  as 
steep  as  1  in  14  or  7|  per  cent  and  in  12  or  8J  per  cent. 

Aside  from  tractive  force,  grade  is  an  important  factor  in  that 
wet  weather  causes  the  pavement  to  become  slippery,  offering 
a  poor  foothold,  and  requiring  the  use  of  sand.  The  frequency 
with  which  it  must  be  scattered  increases  with  the  grade  and  is  an 
additional  expense  in  the  item  of  maintenance. 

On  grades  exceeding  five  per  cent  the  blocks  should  be 
grooved  or  laid  with  wide  joints  which  are  filled  with  asphaltic 
cement  and  gravel,  sand  or  cement  grout  as  shown. 

The  transverse  contour  should  conform  in  outline  to  the  arc 
of  a  circle  or  parabola,  and  should  drop  from  centre  to  sides  an 
amount  equal  to  one-eightieth  to  one-hundredth,  the  total  width 
of  wheelway. 

CAUSES  OF  FAILURE.     The  chief  causes  of  failure  are  a  poor 


282  HIGHWAY   ENGINEERING 

foundation,  difficulty  in  preventing  the  water  from  getting  into 
the  foundation  at  the  curb,  or  leaking  through  the  joints,  and  the 
splitting  of  the  blocks. 

To  offset  this,  the  foundation  should  be  unyielding  and  im- 
pervious, the  timber  should  be  sound,  well  seasoned,  and  non- 
absorptive  in  character,  and  finally  the  joint  filling  should 
prevent  moisture  getting  at  the  foundation. 

VALUE  OF  PRESERVED  WOOD  FOR  PAVEMENTS.  Impregnated 
woods  should  be  used  only  when  the  pavement  wears  out  slowly, 
as  the  preservative  protects  wood  from  decay.  If  wear  is  rapid, 
then  the  wood  wears  out  before  it  begins  to  decay,  and  it  is  there- 
fore unnecessary  to  treat  the  block  unless  such  treatment  of  the 
block  adds  to  the  strength  and  life  of  the  pavement.  Soft-wood 
paverrients  last  6  to  7  years,  while  hard-wood  pavements,  10  to 
12  years.  Soft  wood  is  more  expensive  to  repair,  though  it  is 
cheaper  in  its  first  cost. 

Complete  Specifications  follow : 

THE  CITY  OF  NEW  YORK,  OFFICE  OF  THE  PRESIDENT  OF  THE 
BOROUGH    OF    MANHATTAN,  BUREAU    OF    HIGHWAYS. 

Specifications  for  Regulating,  Grading,  and  Paving  or  Repairing 
with  Wood-Block  Pavement  on  a  Concrete  Foundation  the 

Roadway  of  ....  from    ....    to    together   with   the 

work  incidental  thereto. 

1.  EXTENT  OF  WORK. — This  shall  consist  of  (1)  taking  up  the 
necessary  curb,  bridgestone,  and  such  portions  of  the  pavement 
that  may  be  required  to  be  removed  for  the  proper  laying  of  the 
pavement ;  (2)  excavating  the  necessary  portions  of  the  roadway 
of  subsoil,  rock,  or  masonry  where  the  same  is  above  the  proper 
subgrade  or  where  the  material  underlying  is  not  of  proper  char- 
acter; (3)  filling  in  depressions  or  openings  in  the  roadway  wher- 
ever said  depressions  are  below  the  grade  aforesaid  or  have  been 
caused  by  the  removal  of  improper  material ;  (4)  laying  concrete 


MODERN  WOODEN  PAVEMENTS  283 

as  a  foundation,  as  has  been  designated ;  (5)  resetting  catch-basins 
and  resetting  or  furnishing  and  setting  city  manhole  heads  to  grade ; 
(6)  furnishing  and  setting  and  redressing  and  resetting  the  neces- 
sary curbstones  and  heading  stones  as  required;  (7)  furnishing 
all  the  materials  for  and  laying  a  wood-block  pavement  in  the 
roadway;  (8)  readjusting  and  relaying  pavement  and  resetting; 
curbstones  in  the  approaches  of  intersecting  streets  and  avenues ;. 
all  to  be  in  accordance  with  the  plan  and  profile  of  the  said  street,, 
now  on  file  in  the  Bureau  of  Highways,  with  workmanship  and 
materials  equalling  in  every  respect  the  requirements  of  these 
specifications  and  the  samples  accepted. 

2.  Material  furnished  and  work  done  not  in  accordance  with 
these  specifications,  in  the  opinion  of  the  engineer,  shall  be  im- 
mediately removed  and  so  replaced  or  corrected  as  to  be  in  ac- 
cordance therewith. 

3.  ESTIMATE  OF  QUANTITIES. — The  estimates  of  the  engineer 
of  the  quantity  and  quality  of  the  supplies  required,  and  the  na- 
ture and  the  extent,  as  near  as  possible,  of  the  work,  are  herein 
stated  and  set  forth. 

square  yards  of  wood-block  pavement. 

cubic  yards  of  concrete,  including  mortar  bed. 

linear  feet  of  new  curbstone,  furnished  and  set. 

linear  feet  of  old  curbstone  redressed,  rejointed, 

and  reset. 

noiseless  covers,  complete  for  water  manholes, 

to  be  furnished  and  set. 

noiseless  covers,  complete,  for  sewer  manholes, 

to  be  furnished  and  set. 

square  yards  of  old  stone  blocks  to  be  pur- 
chased by  contractor  and  removed. 

4.  PERSONAL  EXAMINATION  OF  WORK. — Bidders  must  satisfy 
themselves  by  personal  examination  of  the  location  of  the  pro- 
posed work,  and  by  such  other  means  as  they  may  prefer,  as  to 
the  accuracy  of  the  foregoing  statement,  and  they  shall  not,  at 


284  HIGHWAY   ENGINEERING 

any  time  after  the  submission  of  their  bid,  dispute  or  complain  of 
such  statement  or  estimate  of  the  engineer,  nor  assert  that 
there  was  any  misunderstanding  in  regard  to  the  nature  or 
amount  of  the  work  to  be  done. 

5.  WORK  TO  COMMENCE  ONLY  WHEN  ORDERED  ON. — No  work 
will  be  paid  for  which  is  done  before  the  contractor  is  ordered  to 
proceed. 

6.  PROSECUTION  OF  WORK. — The  work  under  this  contract 
shall  be  prosecuted  at  and  from  as  many  different  points,  at  such 
times,  and  in  sections  of  such  length  along  the  line  of  the  work 
and  with  such  force  as  the  president  may,  from  time  to  time,  dur- 
ing the  progress  of  the  work,  determine,  at  each  of  which  points 
inspectors  may  be  placed  to  supervise  the  same. 

7.  MATERIAL   NOT  TO  OBSTRUCT  TRAVEL. — During  suspen- 
sions all  materials  delivered  upon,  but  not  placed  in  the  work 
shall  be  neatly  piled  so  as  not  to  obstruct  public  travel,  or  shall  be 
removed  from  the  line  of  the  work  at  the  direction  of  the  engineer, 
and  unless  the  materials  be  so  removed  by  the  contractor  upon 
notice  from  the  engineer,  the  materials  may  be  removed  by  the 
president  and  the  expense  thereof  charged  to  the  contractor. 

8.  ENCUMBRANCES. — The  contractor  shall  remove  at  his  own 
expense,  when  directed  by  the  engineer,  any  encumbrances  or 
obstructions  on  the  line  of  the  work,  located  or  placed  there  prior 
to  or  after  its  commencement. 

9.  CONTRACTOR  NOT  TO  DISTURB  CITY  MONUMENTS. — The 
contractor  shall  not  excavate  around  such  city  monuments  and 
bench-marks  as  may  come  within  the  limits  of,  or  be  disturbed  by 
the  work  herein  contemplated  nearer  than  five  (5)  feet  or  in  any 
manner  disturb  the  same,  but  shall  cease  work  at  such  locations 
until  the  said  monuments  or  marks  have  been  referenced  and 
reset  or  otherwise  disposed  of  by  the  president.     The  necessary 
labor  to  remove,  care  for,  and  reset  all  such  monuments  arid  bench- 
marks shall  be  furnished  without  charge  therefor  by  the  con- 
tractor. 


MODERN  WOODEN  PAVEMENTS  285 

10.  MANHOLES,  ETC.,  TO  BE  RESET. — Such  catch-basins,  man- 
hole frames  and  heads  for  sewers,  waterpipes  or  other  conduits 
belonging  to  the  City  on  the  line  of  the  work  as  may  be  designated 
shall  be  reset  to  the  new  grades  and  lines  by  the  contractor  with- 
out extra  charge  therefor;   and  they  shall  be  brought  to  such 
grades  with  brick  masonry  of  the  same  thickness  as  that  originally 
used,  laid  in  hydraulic  cement  mortar  and  the  cost  thereof  shall 
be  included  in  the  price  bid  for  the  contiguous  pavement.     Noise- 
less covers,  complete,  with  interchangeable  ventilating  and  non- 
ventilating  fittings,  for  water  and  sewer  manholes,  of  the  design 
approved  by  the  engineer,  shall  be  furnished  and  set  when  re- 
quired, in  the  manner  above  designated.     All  other  manholes  and 
boxes  are  to  be  reset  to  the  proper  grade,  under  the  contractor's 
direction,  by  the  companies  owning  the  same. 

11.  The  grades  of  all  manholes  and  boxes  must  conform  ab- 
solutely to  that  of  the  pavement  surrounding,  and  the  contractor 
shall  supervise  and  see  that  all  such  resetting  is  substantially  and 
accurately  done  in  conformity  with  the  foregoing,  whether  such 
resetting  shall  be  done  by  his  own  men  or  by  those  from  other 
companies,  and  he  shall  report  hi  writing  to  the  engineer  any 
disinclination  or  negligence  on  the  part  of  the  latter  to  perform 
their  work  properly. 

12.  The  contractor  will  be  held  strictly  accountable  for  any 
variation  or  difference  between  the  grades  of  reset  manholes  and 
boxes  and  that  of  the  contiguous  pavement,  and  any  such  differ- 
ence existing  on  the  completion  of  the  work,  or  occurring  during 
the  maintenance  period  thereof,  shall  be  corrected  by  the  con- 
tractor at  his  own  expense. 

13.  MATERIALS   TO    BE   REMOVED. — BRIDGESTONES   TO    BE 
LOADED. — OLD  CURBSTONES. — All  old  materials  necessary  to  be 
removed  in  the  preparation  for   paving,  excepting    manhole 
heads  and  boxes  and  the  materials  herein  mentioned,  shall  be 
the  property  of  the  contractor,  and  shall  be  immediately  removed 
by  him  off  the  line  of  the  work.     Bridgestones  that  are  to  be  used 


286  HIGHWAY   ENGINEERING 

again  shall  be  neatly  piled,  as  hereinafter  set  forth,  and  such  as 
are  riot  so  required,  and  all  removed  manhole  heads  and  boxes, 
shall  be  loaded  by  the  contractor  into  the  carts  or  wagons  of  the 
Bureau  of  Highways  and  shall  remain  the  property  of  the  City. 
Old  curbstones  which  cannot  be  utilized  in  accordance  with  the 
terms  of  these  specifications  shall  become  the  property  of  the 
contractor,  to  be  disposed  of  by  him. 

14.  MATERIALS  TO  BE  USED  AGAIN. — PRICE  FOR  PAVEMENT 
TO  INCLUDE  REMOVAL. — Such  other  material  which  is  specially 
suitable  for  use  in  the  work  shall  be  collected,  piled,  and  utilized 
as  directed  by  the  engineer.     All  the  work  of   removing   and 
loading  old  material,  as  above,  shall  be  included  in  the  price  bid 
per  square  yard  of  pavement. 

15.  EXCAVATION  AND  FOUNDATION. — The  old  paving  blocks 
and  other  materials  necessary  to  be  removed  shall  be  taken  up 
and  disposed  of,  as  required,  and  the  roadways  excavated  of  all 
subsoil  or  other  matter,  be  it  earth,  rock,  or  other  material,  to  a 
uniform  subgrade  eight  (8)  inches  below  the  top  of  the  finished 
pavement,  or  to  such  other 'depth  as  the  engineer  may  require. 
No  ploughing  will  be  allowed  within  six  (6)  inches  of  such  sub- 
grade,  except  by  permission  of  the  engineer. 

16.  SPONGY  MATERIAL. — All  spongy  or  objectionable  matter 
disclosed  by  the  excavations  thus  made  shall  be  removed  and  the 
space  filled  with  acceptable  material,  compacted  by  thorough 
ramming. 

17.  ROLLING. — UNSATISFACTORY  MATERIAL  TO  BE  USED. — 
When  required,  the  entire  roadbed,  after  having  been  brought  to 
the  necessary  subgrade,  shall  be  rolled  with  a  steam  roller  until 
the  surface  is  thoroughly  compacted  and  the  inaccessible  portions 
shall  be  tamped,  wetted,  and  tamped  or  rolled  with  a  small  roller 
and  wetted,  as  may  be  directed.     Material  not  admitting  of 
satisfactory  rolling  shall  be  removed,  and  such  new  material  as 
may  be  necessary  to  replace  the  same  or  bring  the  pavement  to 
the  proper  grade  shall  be  supplied  and  placed  by  the  contractor 


MODERN  WOODEN  PAVEMENTS  287 

without  extra  compensation  therefor.  It  shall  be  good,  whole- 
some earth,  free  from  foreign  matter,  and  shall  be  placed  in  layers 
not  more  than  six  (6)  inches  in  depth  and  rolled  or  rammed  as 
above  or  as  may  be  directed. 

18.  ROADBED  SHAPING. — Great  care  shall  be  exercised  in 
shaping  the  roadbed  to  secure  a  uniform  surface  parallel  to,  and 
the  required  depth  below  the  given  grade  and  crown,  and  the 
entire  cost  of  such  excavation  and  shaping  shall  be  included  in  the 
price  paid  for  pavement. 

19.  CONCRETE  FOUNDATION. — On  the  roadbed  thus  prepared 
shall  be  laid  a  concrete  foundation  of  the  materials  and  thickness 
set  forth  in  these  specifications. 

20.  DELIVERY  OF  MATERIAL  AND  INSPECTION. — The  materials 
for  construction  shall  not  be  brought  to  or  deposited  on  the  street 
in  quantities  greater  than  is  necessary  for  convenient  working, 
and  shall  be  so  deposited  as  to  cause  the  least  possible  obstruction 
to  streets  and  sidewalks,  as  may  be  determined  by  the  engineer. 
All  new  material  of  every  description  shall  be  carefully  in- 
spected after  it  is  brought  on  the  street,  and  all  such  not  con- 
forming in  quality  and  dimensions  to  these  specifications  will 
be  rejected  and  must  be  immediately  removed  from  off  the  line 
of  the  work. 

21.  ASSISTANCE  TO  BE  FURNISHED. — The  contractor  shall 
furnish  such  laborers  as  may  be  necessary  to  aid  the  engineer 
in  such  examinations,  and  in  case  he  shall  neglect  or  refuse  so  to 
do,  such  laborers  as  may  be  necessary  will  be  employed  by  the 
president  and  the  expense  therefor  will  be  deducted  from  and 
paid  out  of  any  money  then  due  or  which  may  thereafter  become 
due  to  the  said  contractor  under  this  agreement. 

22.  PILING  OF  MATERIAL. — All  old  and  such  new  material  as 
has  been  approved,  except  sand  and  broken  stone,  shall  be  neatly 
piled  by  the  contractor  on  the  front  half  of  the  sidewalk,  on  planks 
not  less  than  one  (1)  inch  thick  if  the  same  be  flagged  or  other- 
wise improved,  not  within  ten  (10)  feet  of  any  fire  hydrant  and 


288  HIGHWAY   ENGINEERING 

with  sufficient  passageways  to  permit  of  free  access  from  the 
roadway  to  each  and  every  house  on  the  line  of  the  work. 

23.  Not  until  this  has  been  done  and  the  rejected  materials 
removed  entirely  from  the  line  of  the  work,  each  of  which 
conditions  must  be  faithfully  fulfilled,  will  the  contractor  be  per- 
mitted to  proceed  with  the  laying  of  the  pavement. 

24.  OLD  CURBSTONES  THAT  MAY  BE  RESET. — Old  curbstones 
which  can  be  redressed  to  a  top  width  of  not  less  than  four  and 
one-half  (4J)  inches,  are  not  less  than  sixteen  (16)  inches  deep, 
and  are  of  the  quality  hereafter  specified,  shall  be  redressed,  re- 
jointed,  and  reset,  as  directed  below.     All  friable  granite  curb- 
stones shall  be  rejected. 

25.  QUALITY,  DIMENSIONS,  AND  DRESSING  OF  NEW  CURB- 
STONES.— New  curbstones  shall  be  hard,  sound,  fine-grained,  and 
uniform-colored  bluestone,  shall  be  free  from  seams  and  other 
imperfections,  and  shall  be  equal  in  quality  to  the  best  North- 
River  bluestone.     They  shall  be  sixteen  (16)  inches  in  depth, 
from  three  and  one-half  (3J)  to  eight  (8)  feet  in  length,  and  not 
less  than  five  (5)  inches  in  thickness  (except  as  noted  for  bottom 
of  curb),  with  square  ends  of  the  full  average  width.     The  face 
for  a  depth  of  nine  (9)  inches  and  the  top,  on  a  bevel  of  one-half 
( J)  an  inch  in  its  width  of  five  (5)  inches,  shall  be  dressed  to  a  sur- 
face, which  shall  be  out  of  wind  and  shall  have  no  depressions 
measuring  more  than  one-quarter  (J)  of  an  inch  from  a  line  or 
straight  edge  of  the  same  length  as  the  curbstone.     The  remain- 
der of  the  face  shall  be  free  from  projections  of  more  than  one- 
half  (i)  an  inch,  and  the  back  for  three  (3)  inches  down  from 
the  top  shall  have  no  projections  greater  than  one-quarter  (J)  of 
an  inch  measured  from  a  plane  at  right  angles  to  the  top.     The 
bottom  of  the  curb  shall  be  rough-squared  with  a  width  of  not  less 
than  three  (3)  inches. 

The  sample  of  the  curbstone  showing  the  dressing  and  the 
jointing  required  can  be  seen  at  the  office  of  the  chief  engineer 
of  the  Bureau  of  Highways. 


MODERN  WOODEN  PAVEMENTS  289 

26.  JOINTING. — For  the  full  width  of  the  stone  for  a  distance 
down  the  same  as  the  above-mentioned  depth  of  dressed  face 
from  the  top,  and  therebelow  to  the  bottom  for  a  width  of  two 
(2)  inches  back  from  the  face,  the  ends  shall  be  squarely  and 
evenly  jointed.    In  no  case  shall  the  ends  of  the  curbstones  abut- 
ting basin-heads  be  bevelled  off  or  reduced  in  width,  but  recesses 
shall  be  neatly  cut  in  such  basin-heads  without  charge  therefor,  to 
give  square,  close  joints  for  the  width  of  the  stone. 

27.  SETTING. — Each  curbstone  shall  be  set  truly  to  grade  and 
line  and  on  a  face  batter  of  one  (1)  inch  in  its  depth,  or  vertically 
as  shall  be  directed :  it  shall  be  firmly  bedded  and  tamped,  and  the 
rear  to  the  top  back  filled  and  tamped  with  clean,  dry,  gritty 
earth  or  coarse  sand,  free  from  rock  fragments,  or  as  hereinafter 
more  particularly  set  forth,  and  the  vertical  face  joints  of  all  curb- 
stones shall  be  flush  pointed  firmly  with  good  mortar  of  one  part 
of  Portland  cement  and  two  of  sand  from  the  top  of  the  curb  to 
the  top  of  the  foundation  of  the  wood-block  pavement. 

28.  CORNER  CURBSTONES. — Curved  curb  for  corners  shall  be 
cut  with  true  radial  joints  and  set  accurately  to  a  radius  of  six 
(6)  feet  in  three  (3)  foot  lengths,  unless  otherwise  required.     It 
shall  be  paid  for  as  straight  curb,  and  must  comply  in  all  respects 
with  the  above  requirements  therefor. 

29. — The  cost  of  excavation  necessary  for  curb-setting  shall  be 
included  in  the  price  paid  per  linear  foot  of  curb,  and  no  compen- 
sation therebeyond  shall  be  made  or  allowed. 

30.  CURB  ON  CONCRETE. — When  specified,  the  curbstone  afore- 
said shall  be  set  on  a  concrete  foundation,  and  the  price  sub- 
mitted per  linear  foot   for  new  curbstone  shall   include  the 
furnishing  of  the  stone  and  all  the  excavations  necessary  for  the 
concrete  foundations. 

31.  CONCRETE  BED  FOR  CURBSTONES. — The  concrete  foun- 
dation for  curbstone  shall  not  be  less  than  six  (6)  inches  thick  and 
eighteen  (18)  inches  in  width,  and  be  of  the  materials  and  pro- 
portions hereinafter  described  except  that  the  broken  stone  shall 

'9 


290  HIGHWAY   ENGINEERING 

not  be  less  than  one-quarter  (J)  nor  more  than  one  and  one-half 
(1J)  inches  maximum  dimensions;  the  curb  to  be  immediately 
bedded  on  the  centre  thereof  with  a  bearing  for  its  full  length  as 
soon  as  the  concrete  is  laid,  and  it  shall  be  at  once  backed  up 
with  concrete  for  a  width  of  six  (6)  inches,  extending  from  the 
bottom  bed  to  within  four  (4)  inches  of  the  top  of  the  stone. 
The  concrete  so  used  will  be  paid  for  at  the  general  price  bid 
per  cubic  yard  for  concrete. 

32.  FRONT  CONCRETE. — Simultaneously  with  the  backing  up 
in  the  rear,  the  concrete  in  front  of  the  curb  shall  be  carried  up, 
for  the  exposed  width  of  the  bottom  bed,  to  the  elevation  of  the 
bottom  of  the  paving  foundation,  and  so  much  of  said  paving 
foundation  itself  as  may  be  necessary,  for  a  width  not  less  than 
six  (6)  inches  from  the  curb,  shall  be  immediately  laid  to  serve  as 
a  support  for  the  curbstones.     When  set  the  corners  of  the  curb 
at  the  top  shall  be  a  straight  and  true  line,  and  the  upper  and  face 
surfaces  a  plane  surface. 

33.  IN  FRONT  OF  CONCRETE  WALKS. — When  curb  is  set  in 
-front  of  a  monolithic,  cement,  or  concrete  sidewalk,  the  space 

between  the  curb  and  sidewalk  foundation  shall  be  completely 
filled  with  concrete,  similar  to  that  on  which  curb  is  set,  to  within 
two  (2)  inches  of  the  top;  the  remaining  space  to  be  filled  with 
Portland  cement  of  the  quality  hereinafter  specified,  mixed  with 
equal  parts  of  crushed  stone  used  for  the  wearing  surface  of  such 
walks.  The  concrete  used  for  foundation  and  setting  curb- 
stones will  be  paid  for  by  the  cubic  yard,  the  same  as  the  price  bid 
for  concrete,  and  the  dimensions  will  be  based  upon  these  herein- 
before stated. 

34.  REMOVAL  OF  FLAGSTONES. — MONOLITHIC  WALKS. — BACK- 
FILLING.— The  front  course  of  flagstones  when  not  over  four  (4) 
feet  in  width  interfering  with  the  work  of  curb-setting  shall  be 
picked  up  and  be  set  back,  and  after  the  curb  has  been  set  and 
thoroughly  backfilled,  they  shall  be  fitted  in  their  original  posi- 
tion and  the  cut  edge  be  retrimmed  and  rejointed  to  a  true 


MODERN  WOODEN  PAVEMENTS  291 

line  to  give  a  joint,  when  possible,  not  more  than  one-half  (i)  an 
inch  wide  at  the  back  of  the  curb  and  be  so  relaid  to  the  new 
curb  grade  when  such  grade  does  not  differ  more  than  five  (5) 
inches  from  that  originally  existing;  the  stone  to  be  thoroughly 
bedded  and  the  joints  cemented  as  herein  set  forth.  Stone  of  un- 
usual size  and  those  containing  coal-hole  openings,  ventilation, 
or  light  castings  shall  in  no  case  be  disturbed,  but  the  front  edge 
shall  be  re  jointed  to  line,  as  above  in  place.  Monolithic  walks 
shall  be  carefully  cut  off  to  a  true  line,  five  and  one-half  (5J) 
inches  back  of,  and  parallel  to  the  new  curb  line,  and  for  use  in 
such  locations  curbstones  shall  be  selected  of  as  near  as  possible  a 
uniform  width  throughout  its  depth  that  the  foundation  of  the 
walk  may  not  be  unnecessarily  damaged.  The  entire  space  be- 
tween back  of  curb  and  such  walks,  or  stones  that  are  left  in  place 
(except  where  curbstones  are  to  be  set  in  concrete  as  above  de- 
scribed), shall  be  backfilled  with  fine  sand,  free  from  gravel  and 
stones,  to  within  two  (2)  inches  of  the  top  of  the  curbstones, 
water  being  freely  used  to  settle  and  compact  the  same.  The  re- 
maining space  shall  be  filled  with  Portland  cement  mixed  with 
sand  or  stone  as  used  for  such  walks,  to  be  neatly  trowelled  to 
place,  and  the  contact  surfaces  of  stones  and  walks  shall  be 
made  clean  and  wet  while  filling  and  trowelling  the  said  two  (2) 
inches. 

35.  Any  damage  done  by  the  contractor  to  sidewalks  in  curb- 
setting,  handling,  or  in  the  storage  of  materials  shall  be  made 
good  by  him,  at  his  own  expense,  as  shall  be  directed  by  the  engi- 
neer. 

36.  NEW  FLAGGING,  QUALITY  AND  DIMENSIONS. — DRESSING 
OF  FLAGSTONE. — New  flagging  furnished  to  replace  any  broken 
shall  be  of  bluestone  of  even  color  and  best  quality,  and  satis- 
factory to  the  president,  not  less  than  three  (3)  inches  thick, 
even  on  its  face,  free  from  seams,  flaws,  drill-holes,  or  discolora- 
tion, measuring  not  less  than  four  (4)  feet  wide,  and  containing 
not  less  than  twelve  (12)  superficial  feet  or  of  the  same  size  as  that 


292  HIGHWAY   ENGINEERING 

broken,  as  shall  be  directed;  the  stones  to  be  chisel-dressed,  with 
sides  parallel,  on  the  four  edges  a  distance  down  of  one  (1)  inch 
from  the  top  and  at  right  angles  thereto;  except  that,  in  side- 
walks where  stones  of  superior  dimensions  or  quality  are  broken, 
the  replaced  stone  must  be  in  length  and  width  not  less  than  the 
old  stone  and  be  of  the  same  quality  of  material. 

37.  LAYING  OF  FLAGSTONE. — CLEARING  UP. — All  flagging  to 
be  relaid  shall  be  firmly  and  evenly  bedded  to  the  grade  and  pitch 
required,  on  four  (4)  inches  of  steam  ashes,  clean,  gritty  earth  or 
sand,  free  from  clay  or  loam,  and  the  work  brought  to  an  even 
surface,  with  all  joints  close  and  thoroughly  filled  (except  around 
monuments  and  trees),  for  the  full  depth  with  cement  mortar, 
composed  of  equal  parts  of  the  best  Portland  cement  and  clean, 
sharp  sand,  and  left  clean  on  the  surface;  and  all  earth,  debris, 
and  surplus  material  shall  be  removed  from  each  block  and  the 
sidewalks  swept  clean,  as  soon  as  the  work  thereon  has  been 
completed. 

38.  HEADING  STONES. — Wherever  the  new  pavement  abuts 
pavement  of  a  different  character,  and  wherever  directed  to  do 
so,  the  contractor  shall  put  down  bluestone  heading  stones  at 
least  three  (3)  feet  long  and  one  (1)  foot  deep,  and  set  with  full 
bearing  on  a  bed  of  concrete  nine  (9)  inches  wide  and  six  (6)  inches 
deep,  of  the  quality  hereinafter  described.     These  heading  stones 
shall  be  of  good,  sound  bluestone,  free  from  lamination  or  seams. 
They  shall  be  dressed  square  on  top  to  a  good  surface,  free  from 
irregularities,  and  to  a  uniform  width  of  not  less  than  four  and 
one-half  (4J)  inches.     The  ends  shall  be  joined  square  down  to 
give  close  joints,  and  the  bottoms  shall  be  nowhere  less  than 
three  (3)  inches  wide  and  be  cut  to  give  a  full,  square  bearing 
throughout,  and  the  sides  shall  be  free  from  bunches.     These 
stones  shall  be  maintained  by  the  contractor,  and  they  will  be 
paid  for  as  wood-block  surface. 

39.  WOOD-BLOCK  PAVEMENT. — (1)  The  material  to  be  treated 
shall  be  wood  blocks,  which  may  be  either  of  Southern  Long-leaf 


MODERN  WOODEN  PAVEMENTS  293 

Yellow  Pine,  Southern  Black  Gum,  Norway  Pine,  or  Tamarac,  riot 
less  than  ninety  per  cent  of  heart,  of  a  texture  permitting  satis- 
factory treatment  as  hereinafter  specified,  and  is  to  be  subject  to 
inspection  at  the  works  in  the  stick  before  being  sawed  into 
blocks. 

(2)  All  blocks  shall  be  of  sound  timber,  free  from  bark,  loose 
or  rotten  knots,  or  other  defects  which  would  be  detrimental 
to  the  life  of  the  block  or  interfere  with  its  laying.     No  second- 
growth  timber  will  be  allowed. 

(3)  The  paving  blocks  cut  from  the  lumber  above  specified 
shall  be  well  manufactured,  truly  rectangular,  and  of  uniform 
dimensions.     Their  depth  (parallel  to  the  fibre)  shall  be  three 
and  one-half  (3J)  inches.     Their  length  shall  be  not  less  than  six 
(6)  or  more  than  ten  (10)  inches,  and  their  width  shall  be  not 
less  than  three  (3)  nor  more  than  four  (4)  inches,  but  all  blocks 
used  in  any  one  contract  are  to  be  of  the  same  width  and  of  the 
same  timber.     Their  depth  and  width  shall  not  vary  more  than 
one-eighth  (|)  inch  from  the  dimensions  specified  for  any  one 
contract. 

(4)  The  blocks  are  to  be  treated  throughout  with  an  anti- 
septic and  water-proof  mixture,  seventy-five  per  cent  of  which 
shall  be  creosote  or  heavy  oil  of  coal  tar  conforming  to  the  speci- 
fications hereinafter  set  forth,  and  twenty-five  per  cent  of  which 
shall  be  resin  conforming  to  the  specifications  hereinafter  set 
forth.    All  parts  of  each  individual  block  shall  be  thoroughly 
treated,  and  not  less  than  twenty  (20)  pounds  of  the  mixture  per 
cubic  foot  shall  be  injected. 

(5)  In  preparing  the  blocks  to  receive  the  creosote  mixture, 
they  shall  be  placed  in  an  air-tight  cylinder,  in  which  dry  heat,  or 
heat  produced  by  superheated  steam,  is  maintained  and  raised  to 
a  temperature  of  215°  Fahrenheit,  for  1  hour,  for  the  purpose  of 
expelling  moisture;   the  heat  is  then  to  be  increased  until  it  has 
reached  285°  Fahrenheit,  this  heat  being  maintained  for  a  period 
of  3  hours,  or  until  the  block  is  completely  sterilized.     Applica- 


294  HIGHWAY   ENGINEERING 

tion  of  heat  is  then  to  be  stopped  and  the  temperature  of  the 
cylinder  allowed  to  fall  for  1  hour,  or  until  same  has  been  reduced 
to  250°.  A  vacuum  is  then  to  be  applied  until  about  26  ins.  is 
reached,  and  while  under  this  vacuum  the  creosote  mixture  is  to 
be  run  into  the  cylinder  at  a  temperature  of  from  175°  to  260°, 
after  which  hydraulic  pressure  of  not  less  than  200  Ibs.  per  sq.  in. 
is  to  be  maintained  and  raised  until  the  individual  blocks  are 
treated  throughout. 

(6)  The  creosote  oil  is  to  conform  to  the  following  specifica- 
tions when  tested,  as  follows: 

(7)  The  gravity  at  68°  Fahrenheit  shall  be  not  less  than  1.12. 
When  distilled  in  a  retort  with  the  thermometer  suspended  not 
less  than  1  in.  above  the  oil,  it  shall  lose  not  more  than  thirty- 
five  (35)  per  cent  up  to  315°  centigrade,  and  not  more  than  fifty 
(50)  per  cent  up  to  370°  centigrade.     The  oil  is  to  be  free  from 
adulteration;  it  must  not  be  mixed  with  or  contain  any  foreign 
material. 

(8)  The  resin  is  to  be  solid  resin  obtained  from  pine.     It  is 
to  be  reduced  to  a  fine  dust  by  grinding,  and  then  incorporated 
with  the  hot  creosote  oil  in  a  suitable  mixing  tank  until  the 
proper  proportions  are  secured. 

(9)  After  treatment  the  blocks  are  to  show  such  water-proof 
qualities  that,  after  being  dried  in  an  oven  at  a  temperature  of 
120°  for  a  period  of  twenty-four  hours,  weighed  and  then  im- 
mersed in  clear  water  for  a  period  of  twenty-four  hours  and 
weighed,  the  gain  in  weight  is  not  to  be  greater  than  three  (3)  per 
cent. 

40.  ANALYSIS  OF  TREATED  BLOCK. — Fine  turnings  from  the 
block  shall  be  placed  in  a  suitable  extraction  apparatus  and  the 
oil  completely  extracted  therefrom  with  ether  or  carbon  bisul- 
phide. The  oil  so  extracted  shall  be  placed  in  a  suitable  still  and 
distilled.  The  portion  up  to  120°  centigrade,  consisting  of  the 
solvent,  is  to  be  collected  apart.  The  oil  shall  then  be  distilled 
up  to  370°  centigrade.  The  creosote  oil  thus  obtained  must  con- 


MODERN  WOODEN  PAVEMENTS  295 

form  in  all  respects  to  the  requirements  of  Paragraph  39,  Sub- 
division 7. 

41.  INSPECTION  OF  MATERIAL. — The  engineer  shall  have  tests 
and  examinations  made  at  the  contractor's  works  of  the  materials 
and  blocks  proposed  to  be  used,  and  reject  any  or  all  of  such  ma- 
terials and  blocks  as  he  may  consider  not  to  be  in  compliance  with 
these  specifications.     The  borough  president  shall  appoint  an  in- 
spector at  the  expense  of  the  contractor,  who  shall  inspect  the 
lumber  and  other  materials  used  in  the  manufacture  of  the  blocks 
and  the  treatment  of  the  blocks;  and  he  shall  reject  any  of  such 
material  and  blocks  as  he  may  consider  not  to  be  in  compliance 
with  these  specifications. 

42.  INSPECTION. — The  blocks  will  be  carefully  inspected  after 
they  are  brought  on  the  line  of  work,  and  all  blocks  which  hi 
quality  and  dimensions  do  not  conform  strictly  to  the  require- 
ments will  be  rejected  and  must  be  immediately  removed  from 
the  line  of  work. 

43.  CEMENT. — The  cement  shall  be  of  the  best  quality  of 
American  Portland,  samples  of  which  must  be  submitted  at  least 
ten  (10)  days  (holidays  and  Sundays  excluded)  before  using,  for 
the  inspection  and  approval  of  the  chief  engineer,  and  no  change 
from  such  approved  brand  shall  thereafter  be  made  without  the 
submission  and  approval  of  samples.     It  will  be  required  that  the 
various  deliveries  shown  by  samples  taken  from  the  work  during 
its  continuance  shall  exhibit  qualities  equal  or  superior  to  those 
developed  by  the  samples  submitted  as  aforesaid. 

44.  QUALITY. — TENSILE  STRENGTH. — All  cements  shall  be 
freshly  ground  and  of  a  uniform  quality,  color,  and  weight, 
and  briquettes  of  one  (1)  square  inch  section  shall  develop  or  ex- 
ceed the  following  tensile  strength : 

Neat,  one  hour  air,  twenty-three  (23)  hours  in  water,  200  Ibs.; 
neat,  one  day  air,  six  (6)  days  in  water,  400  Ibs. ;  neat,  one  day 
air,  twenty-seven  (27)  days  in  water,  480  Ibs. ;  one  of  Portland, 
three  (3)  of  sand,  one  day  air,  six  (6)  days  water,  150  Ibs. 


296  HIGHWAY  ENGINEERING 

45.  CONCRETE. — PROPORTIONS  OF  MATERIALS. — THE  UNIT 
OF  MEASURE. — The  concrete  shall  be  composed  of  one  (1)  part  of 
cement,  three  (3)  parts  of  sand,  and  six  (6)  parts  of  broken  stone, 
but  should  the  proportion  of  voids  in  the  stone  be  such  that  a 
greater  or  less  quantity  of  stone  be  required  to  give  satisfactory 
results,  the  amount  of  broken  stone  shall  be  increased  or  de- 
creased to   the  extent  directed    by  the   engineer   upon   any 
particular  piece  of  work.    The  unit  of  measure  shall  be  the 
barrel  of  cement  as  packed  by  and  received  from  the  man- 
ufacturer. 

46.  SAND  AND  BROKEN  STONE. — To  BE  STORED  ON  PLAT- 
FORMS.— The  sand  shall  be  clean,  coarse,  and  sharp,  and  be  free 
from  loam  or  dirt.     The  broken  stone  shall  be  of  trap,  granite,  or 
limestone,  or  such  other  stone  taken  from  the  line  of  the  work  as 
shall  be  satisfactory  in  the  judgment  of  the  engineer.     It  shall  be 
entirely  free  from  dust  and  dirt,  and  be  of  graded  sizes  that  will 
pass  in  any  direction  through  a  revolving  circular  screen  having 
holes  two  and  one-half  (2J)  inches  in  diameter,  and  be  retained 
by  a  screen  having  holes  one  (1)  inch  in  diameter.    The  sand  and 
stone  must  be  placed  upon  board  platforms  and  kept  free  from 
dirt,  and  the  cement  shall  be  properly  blocked  up  and  protected 
from  dampness. 

47.  SIZE  OF  BATCH. — MIXING. — USE  OF  MIXING  MACHINE. — 
Concrete,  unless  machinery  be  used,  shall  be  mixed  in  batches, 
containing  not  more  than  one  (1)  barrel  of  cement  with  the  req- 
uisite proportion  of  other  material,  on  suitable  tight  platforms, 
not  less  than  twelve  (12)  feet  by  twelve  (12)  feet  in  size.     The 
cement  and  sand  shall  be  thoroughly  mixed  dry  after  which  the 
broken  stone,  having  first  been  wetted,  shall  be  added.     The 
whole  mass  shall  then  be  turned  and  worked  by  skilled  laborers, 
until  a  resultant  is  obtained,  with  the  stone  uniformly  distributed. 
In  shovelling,  the  material  must  be  lifted  clear  of  the  board.     If  a 
concrete  mixing  machine  be  used,  the  cement  and  sand  shall  be 
mixed  as  above  and  precautions  taken  to  insure  the  proper 


MODERN  WOODEN  PAVEMENTS  297 

proportion  of  each  of  the  materials,  so  that  the  resultant  mixture 
shall  be  uniform  in  quality. 

48.  LAYING. — CONCRETE  SURFACE  TO  BE  SCABBLED. — The 
concrete  shall  be  placed  in  position,  and  there  rammed  with 
proper  rammers  until  thoroughly  compacted.     The  whole  opera- 
tion of  mixing  and  laying  each  batch  must  be  performed  as  ex- 
peditiously  as  possible,  and  in  no  case  shall  concrete  be  used  which 
has  been  mixed  more  than  one-quarter  (J)  of  an  hour.     The  con- 
crete shall  be  protected  from  the  weather  until  set,  and  should  it 
at  any  time  be  considered  by  the  engineer  to  be  poorly  mixed  or 
not  to  be  setting  properly,  such  portions  shall  be  taken  up  and 
replaced  with  satisfactory  material.     Sufficient  time,  of  which 
the  engineer  shall  be  the  judge,  shall  be  allowed  for  the  concrete 
to  set  before  the  pavement  is  laid  thereon.     Before  laying  con- 
crete to  connect  with,  rest  upon,  or  overlap  any  concrete  pre- 
viously laid,  the  entire  surface  of  contact  of  the  latter  shall  be 
swept  and  washed  clean  of  all  dirt  and  mortar  particles  and,  when 
deemed  necessary,  shall  be  satisfactorily  scabbled. 

49.  No  TRAFFIC  ON  CONCRETE. — No  horses,  carting,  or  wheel- 
ing shall  be  allowed  on  the  concrete  until  the  same  has  thoroughly 
set,  and  then  only  on  planks  furnished  and  laid  by  the  contractor. 
By  car  tracks  the  contractor  shall  provide  men  to  pass  cars  there- 
over. 

50.  THICKNESS  AND  TESTING. — The  concrete  foundation  shall 
be  four  and  one-half  (4J)  inches  thick,  including  a  mortar  top 
surface  of  one-half  (J)  inch  in  thickness,  the  concrete  proper  being 
four  (4)  inches  thick,  and  shall  withstand  such  tests  as  the  engi- 
neer may  deem  necessary,  and  the  contractor  shall  furnish  such 
samples  as  may  be  required  for  the  purpose. 

51.  CEMENT  MORTAR  BED. — Upon  the  surface  of  the  concrete 
foundation  shall  be  spread  a  bed  of  cement  mortar  one-half  inch 
in  thickness.     This  mortar  surface  shall  be  composed  of  a  slow- 
setting   Portland   cement   and   clean,   sharp   sand,   free   from 
pebbles  over  one-quarter  (J)  inch  in  diameter,  and  mixed  in  the 


298  HIGHWAY  ENGINEERING 

proportion  of  one  part  cement  to  four  parts  of  sand.  This  mor- 
tar top  shall  be  thoroughly  rammed  into  place  with  concrete 
rammers  until  all  the  unevenness  in  the  concrete  shall  be  taken 
up,  and  shall  then  be  "  struck  "  to  a  true  surface  exactly  parallel 
to  the  top  of  the  finished  pavement. 

52.  On  the  surface  of  the  concrete  foundation  before  the  mor- 
tar bed  is  laid  shall  be  set  strips  of  wood  four  (4)  inches  wide  by 
one-quarter  ( J)  inch  thick,  or  strips  of  steel  four  (4)  inches  wide 
by  not  less  than  one-eighth  (-J-)  inch  thick,  and  of  the  greatest 
length  convenient  for  handling.     These  strips  shall  be  carefully 
set  parallel  and  about  eight  (8)  or  ten  (10)  feet  apart,  running 
from  curb  to  curb,  and  be  embedded  in  mortar  throughout  their 
length  so  that  the  top  surface  shall  be  three  and  one-half  (3J) 
inches  below  and  parallel  to  the  grade  of  the  finished  pavement. 
The  space  between  two  strips  having  been  filled  with  mortar,  a 
true  and  even  top  surface  shall  be  struck  by  using  an  ironshod 
straight  edge  on  the  strips  as  a  guide,  and  as  soon  as  the  bed  has 
been  struck,  the  strip  which  would  interfere  with  laying  the  blocks 
shall  be  removed  and  its  place  carefully  filled  with  mortar  with  a 
trowel. 

53.  If  the  width  of  the  roadway  be  such  that  the  laying  of 
blocks  on  a  complete  section  cannot  be  completed  before  the 
mortar  takes  its  initial  set,  the  strips  may  be  placed  parallel  to 
the  curb,  and  templates  cut  to  the  curve  of  the  desired  crown 
shall  be  used  on  these  strips  to  strike  the  bed. 

54.  METHOD  OF  LAYING. — On  this  mortar  surface  spread  and 
smoothed  as  above  to  the  proper  crown  and  grade,  the  blocks  are 
to  be  laid  with  the  grain  vertical  and  at  such  an  angle  with  the 
curb  as  the  engineer  may  direct.     They  shall  be  laid  in  parallel 
courses  with  as  tight  joints  as  possible,  each  block  being  firmly 
bedded  in  the  mortar  bed  so  as  to  form  a  true  and  even  surface. 
A  one-half  inch  paving  expansion  joint  shall  be  used  along  each 
curb  and  across  the  street  every  one  hundred  feet. 

The  joints  shall  then  be  filled  with  cement  grout  composed  of 


MODERN  WOODEN  PAVEMENTS  299 

2  parts  clean  sand  and  1  part  of  Portland  cement,  mixed  to 
a  perfectly  liquid  form,  and  the  surface  of  the  block  shall  be 
slushed  with  same  and  the  joints  swept  until  they  are  com- 
pletely filled.  The  surface  shall  then  be  covered  with  }  in.  of 
screened  sand. 

55.  GROOVED  BLOCKS. — Where  wood-block  pavement  is  laid 
on  streets  or  parts  of  streets  having  a  gradient  of  more  than  three 
per  cent  the  blocks  shall  be  not  less  than  six  (6)  inches  nor  more 
than  ten  (10)  inches  long,  and  the  upper  edge  of  each  block 
shall  be  cut  away  for  a  width  of  one-fourth  (J)  inch  and  a  depth 
of  one  (1)  inch,  so  as  to  provide  transverse  grooves  of  that  width 
and  depth  between  each  course  of  block  when  the  blocks  are  laid 
in  place;  or  such  other  construction  shall  be  used  as  will,  in  the 
opinion  of  the  engineer,  provide  an  equally  good  foothold  for 
horses. 

56.  CUTTING  CLOSURES. — Nothing  but  whole  blocks  shall  be 
used  except  in  starting  a  course  or  in  sucli  other  cases  as  shall 
be  specially  permitted  by  the  engineer,  and  in  no  case  shall  less 
than  one-third  of  a  block  be  used  in  breaking  joints.     Closures 
shall  be  carefully  cut  and  trimmed  by  experienced  men,  the  por- 
tion of  the  block  to  be  used  to  be  free  from  check  or  fracture  and 
the  cut  end  to  have  a  surface  normal  to  the  top  of  the  block  and 
be  cut  at  the  proper  angle  to  give  a  close,  tight  joint. 

57.  LAYING. — Each  course  of  blocks  shall  be  of  uniform  width 
and  depth,  with  all  joints  close  and  the  end  joints  broken  by  a 
lap  of  at  least  four  (4)  inches,  and,  while  laying,  the  pavers  must 
stand  on  those  already  laid.     Any  lack  of  uniformity  in  the  sur- 
face or  unevenness  in  the  blocks  must  be  immediately  corrected 
by  taking  up  and  relaying  the  blocks,  and  blocks  fractured  or 
broken  shall  be  replaced  with  perfect  ones  before  any  sand  is 
spread  over  the  surface. 

58.  SAND  COVERING. — When  laid,  the  blocks  shall  be  covered 
with  clean,  fine  sand,  entirely  free  from  loam  or  earthy  matter, 
perfectly  dry  and  screened  through  a  sieve  having  not  less  than 


300  HIGHWAY  ENGINEERING 

twenty  (20)  meshes  per  linear  inch,  the  sand  to  be  left  on  the 
surface  until  such  time  when,  if  required  by  the  engineer,  the  pave- 
ment shall  be  swept  clean  for  final  inspection  and  any  defects  then 
noted  shall  be  remedied. 

59.  READJUSTMENT  OF  ADJOINING  PAVEMENT. — The  curb- 
stones and  gutters  of  the  adjoining  pavements,  and  all  pave- 
ments abutting  the  new  work,  shall  be  readjusted  and  brought 
to  the  new  grades  and  lines  to  the  extent  deemed  necessary  by  the 
engineer,  and  such  readjustment  of  curb  and  pavement  shall  in- 
clude rejointing,  resetting,  and  relaying  as  herein  provided,  all 
without  charge  therefor. 

60.  In  readjusting  such  abutting  pavements,  all  imperfect 
stones  shall  be  discarded  and  only  those  of  regular  shape  used 
and  before  the  old  pavement  of  the  street  being  paved  shall  have 
been  removed,  the  contractor  shall  select  therefrom  enough  per- 
fect stones,  and  preserve  the  same  until  needed,  to  make  up  any 
deficiencies.     On  the  contractor's  failure  so  to  do,  he  shall  pro- 
vide such  extra  necessary  stones  at  his  own  expense  and  to  the 
satisfaction  of  the  engineer. 

61.  The  stones  shall  be  laid  in  straight  and  regular  courses, 
with  close  end  joints  broken  by  a  lap  of  at  least  three  inches.  The 
joints  between  courses  shall  be  close  except  when  gravel  filling 
is  to  be  used,  and  the  courses  shall  be  carried  parallel  to  the  exist- 
ing courses;  any  differences  in  alignment  between  such  courses 
and  the  header  shall  be  corrected  at  the  header  by  neatly  trim- 
ming the  blocks.    None  but  stones  of  the  same  width  shall  be 
used  in  the  same  course  except  where  trimming  is  necessary. 

62.  All  stones  shall  be  relaid  on  a  full  bed  of  sand  and  be 
thoroughly  rammed  to  a  firm  unyielding  bearing  and  to  a  uni- 
form surface,  the  joints  to  be  brushed  full  of  sand. 

63.  When  the  pavement  is  to  be  relaid  on  a  concrete  founda- 
tion with  joint  filling,  such  foundation,  if  required  by  the  engineer, 
shall  be  removed  and  relaid,  or  be  added  to  with  concrete,  as  may 
be  necessary;  all  other  detail  to  be  in  accordance  with  the  cur- 


MODERN  WOODEN  PAVEMENTS  301 

rent  specifications  for  similar  work  in  use  in  the  Bureau  of 
Highways. 

64.  REMOVAL  OF  SURPLUS  MATERIALS,  RUBBISH,  ETC. — All 
surplus  materials,  earth,  sand,  rubbish,  and  stones  are  to  be  re- 
moved from  the  line  of  the  work,  block  by  block,  as  rapidly  as  the 
work  progresses;  all  material  covering  the  pavement  and  side- 
walks shall  be  swept  into  heaps  and  immediately  removed  from 
the  line  of  the  work;  and  unless  this  be  done  by  the  contractor 
within  forty-eight  hours  after  being  notified  so  to  do,  by  written 
notice  to  be  served  upon  the  contractor,  either  personally  or  by 
leaving  it  at  his  residence  or  with  any  of  his  agents  on  the  work, 
to  the  satisfaction  of  the  president,  the  same  shall  be  removed 
by  the  said  president  and  the  amount  of  the  expense  thereof  shall 
be  deducted  out  of  any  moneys  due  or  to  grow  due  to  the  con- 
tractor under  this  agreement. 

65.  SWEEPING  AND  SPRINKLING. — At  all  times  during  the 
prosecution  of  the  work,  such  materials  as  may  be  placed  on  the 
sidewalk  shall  be  piled  in  the  manner  heretofore  set  forth,  and  the 
contractor  shall  keep  the  footway  clean  by  sweeping.     When 
such  material  is  removed,  the  sidewalk  must  be  immediately  swept 
clean  by  the  contractor,  and  when  public  or  local  inconvenience 
is  caused  by  dust,  the  contractor  shall  water  any  piles  or  surfaces 
of  earth  or  the  sidewalks  or  pavement  foundation  during  sweep- 
ing, when  and  where  necessary  or  whenever  required  by  the 
engineer  so  to  do. 

66.  PATENTED  ARTICLES. — That  whenever  or  wherever  an 
article  or  any  class  of  materials  is  specified  by  the  name  of  any 
particular  patentee,  manufacturer,  or  dealer,  or  by  reference  to 
the  catalogue  of  any  such  manufacturer  or  dealer,  it  shall  be  taken 
as  intending  to  mean  and  specify  the  article  or  materials  de- 
scribed, or  any  other  equal  thereto  in  quality,  finish,  and  dura- 
bility and  equally  as  serviceable  for  the  purposes  for  which  it 
is  (they  are)  intended.     Nothing  in  these  specifications  shall  be 
interpreted  or  taken  to  violate  the  provisions  of  Section  1554  of 


302  HIGHWAY  ENGINEERING 

the  Greater  New  York  Charter,  which  provides  that  "  except  for 
repairs  no  patented  pavement  shall  be  laid  and  no  patented 
article  shall  be  advertised  for,  contracted  for,  or  purchased,  ex- 
cept under  such  circumstances  that  there  can  be  a  fair  and 
reasonable  opportunity  for  competition,  the  conditions  to  secure 
which  shall  be  prescribed  by  the  Board  of  Estimate  and  Ap- 
portionment." 


INDEX 

ABANDONMENT  of  contract,  New  Jersey  practise  in  case  of,  65 
Alvord,  J.  W.,  on  brick  pavements,  with  illustrations,  195-197 
Asphalt,  characteristics  and  varieties  of,  222-224 
liquid,  249 
pavement,  block,  232,  233 

block,  composition  and  treatment  of  concrete  for,  267- 

block,  curbing  for,  259,  260 

block,  cutting  closures,  269,  270 

block,  New  York  City  specifications  for,  254-272 

block,  qualities  of  cement  for,  266 

block,  rolling  of,  258 

block,  size  and  composition  of  blocks,  264,  265 

tensile  strength  of,  266 

block,  tests  for,  265,  266 

block,  treatment  of  flagstones,  262,  263 

block,  treatment  of  manholes,  catch-basins,  etc.,  256 

block,  treatment  of  monolithic  walks,  262 

mixture,  composition  and  properties,  248 

proper,  definition,  247 

sheet,  binder  for,  228 

sheet,  broken  stone  for,  242,  243 

sheet,  cement  and  concrete  for,  242 

sheet,  composition  of  mixture,  250 

sheet,  crown  for,  231,  232 

sheet,  flagging  for,  239-242 

sheet,  foundation  for,  227,  228 

sheet,  grade  and  crown,  231,  232 

sheet,  heading  stones  for,  242 

sheet,  process  of  laying,  251 

sheet,  sand  for,  229,  242 

sheet,  specifications  for,  233-253 

sheet,  stone  dust  for,  229 

sheet,  wearing  surface,  229-231 

traction  tests  on,  by  Iowa  State  University,  13 

pavements,  222  et  seq. 

advantages  and  disadvantages,  226 

artificial,  226 

natural,  225 

303 


304 


INDEX 


Asphaltic  cement  for  sheet  asphalt  pavement,  230,  231 

properties  and  requirements,  249,  250 
Asphalts,  rock,  requirements  of,  when  used,  251 
Axle-trees  and  wheels,  arrangement  of,  to  prevent  ruts,  118,  119 

BACKFILLING  in  block  asphalt  work,  262 

Baker,  table  showing  effect  of  grade  and  road  covering  on  load,  23 

Baker's  coefficient  of  axle  friction,  2 

Ball  mill  in  stone-dust  preparation  for  briquettes,  with  illustration,  99,  100 

Batch,  size  of,  in  mixing  concrete  for  block  asphalt  work,  267 

Belgian-block  pavement,  177,  178 

origin  of  name,  177 
Bids,  gravel  road,  New  Jersey  requirements,  61 

New  Jersey  practice,  134 
Binder  for  gravel  roads,  47 

for  sheet  asphalt  pavements,  228 

Binders  for  macadam  or  telford,  New  Jersey  practice,  130 
Binding  material  for  macadam  road,  Macadam's  opinion,  124 
Black,  Prof.  A.,  article  on  tests  of  road  stone,  81-91 
Block  asphalt  pavement,  see  Asphalt  pavement,  block 
Blocks,  asphalt,  size  and  composition,  264,  265 

tests  for,  265,  266 
city,  desirable  size  of,  164 
Brick  for  paving,  sizes  and  qualities,  195-197,  214 

paving,  testing  for  hardness,  Moh's  scale,  198 
pavement,  advantages  of,  194,  195 

J.  W.  Alvord  on,  195,  197 

traction  tests  on,  Iowa  State  University,  13 
pavements,  curbing,  210,  211 

"Directions  for  Laying,"  etc.,  recommended  by  the  National  Pav- 
ing Brick  Manufacturers  Association,  209-221 

expansion  cushion  for,  217 

foundation  for,  202,  203,  212 

history,  description,  etc.,  194  et  seq. 

imperviousness  and  density  of  material,  202 

intersections,  with  illustrations,  206-208 

joint  filling  for,  204 

laying  the  brick,  205,  206,  215 

rolling  and  tamping,  218 

testing  for  strength  of  material,  200,  201 

testing  for  toughness  of  material,  198-200 

machine  for,  199 
Bridges,  culverts,  suspension  work,  New  Jersey  practice,  64 

etc.,  in  stone-road  making,  New  Jersey  requirements,  138 
Bridgestones  for  stone  pavements,  243,  244 


INDEX  305 

Bridgestones,  New  York  City  specifications,  189 

cement  for,  190 
Briquettes  in  stone  tests,  descriptions  of,  and  illustrations  of  machines  for 

making,  94-101 
Broken-stone  roads,  description  and  treatment,  70 

roads,  varieties  of,  70 
Burnt-clay  roads  described,  143 

CARRIAGEWAY,  width  of,  165,  166 

Catch-basins,  New  York  City  practice,  184 

Cement  and  concrete  for  sheet  asphalt  pavements,  242 

asphaltic,  properties  and  requirements,  249,  250 

for  block  asphalt  work,  qualities  of,  266 

tensile  strength  of,  266 

wood  pavements,  New  York  City  requirements,  295 

paving,  New  York  City  practice,  191 
temperature,  etc.,  246 

toothing,  246 

Cementation  tests  of  stone  for  roadmaking,  94-102 
Central  Park,  New  York  city,  gutters  in,  170 
Charcoal  roads,  construction  of,  151,  152 
Check  accompanying  bids,  New  Jersey  requirements,  135 

bids  in  gravel  road  specifications,  New  Jersey,  62 
Chemical  treatment  of  blocks  for  wood  pavement,  278 
Chert  in  binder  for  gravel  roads,  48 
Chesapeake  Bay  district,  shell  roads  in,  150 
City  blocks,  desirable  size  of,  164 

streets,  see  Streets 
Clay  on  gravel  roads,  47 

Cleaning  various  pavements,  comparison  of  labor  required,  illustration,  197 
Closures,  cutting,  in  block  asphalt  work,  269,  270 

in  wood  paving,  299 
Coal- slack  roads,  151 
Cobblestone  pavements,  176,  177 
Concrete  and  cement  for  sheet  asphalt  pavement,  242 

for  block  asphalt  work,  composition  and  treatment  of,  267-269 
wood  pavements,  New  York  City  requirements,  296,  297 

foundation  for  curbstone,  186,  187 
Construction  of  gravel  roads,  50-53 
Contour  of  earth  roads,  with  illustrations,  41,  42 
Contract,  subletting,  New  Jersey,  67 

Contractor,  liabilities  of,  New  Jersey  specifications,  136,  137 
Corduroy  roads  described,  143,  144 
Covering,  thickness  of,  for  stone  road,  108-110 
Cross-section  of  stone  road,  113 


306  INDEX 

Crown  of  city  streets,  treatment  of,  172 

earth  roads,  contour  and  treatment  of,  with  illustrations,  41,  42 

gravel  roads,  50 

sheet  asphalt  pavement,  231,  232 

stone  road,  amount  of,  113 

stone  road,  effect  of  grade  on,  table,  114 
Crushing  resistance  of  stone,  determination  of,  102 
Culverts  on  earth  roads,  employment  of,  39 
Curbing  for  block  asphalt  pavement,  259,  260 

brick  pavements,  210,  211 

Curbs  and  gutters  for  city  streets,  with  illustrations,  169-172 
Curbstones  for  stone  pavements,  New  York  City  practice,  185,  186 
Cushion,  expansion,  for  brick  pavements,  217 

DE  CAMP  machine  for  oiling  roads  described  and  illustrated,  147,  148 

Definition  of  asphalt  pavement  proper,  247 

Department  of  Agriculture,  report  to,  of  repairs  to  macadam  roads,  114-122 

Agriculture  tests  at  Cotton  States  Exhibition  in  Atlanta,  14-18 
Deval  machine  in  abrasion  tests,  91 
Diagonal  system  of  city  streets,  Haupt  on,  with  illustrations  and  formulas, 

159-164 

Dirt  roads,  see  Earth  roads 
Ditches  for  gravel  roads,  New  Jersey  practice,  60 

side,  for  earth  roads,  39,  40 

Drags,  varieties  and  uses  of,  with  illustrations,  31,  32 
Drainage  of  earth  roads,  side  ditches  as  factor,  39,  40 

gravel  roads,  49,  50 

stone  roads,  New  Jersey  requirements,  133,  137 

streets,  169-173 

subsurface,  on  earth  roads,  32-38 
Drains  for  earth  roads,  details  of,  illustrations,  33,  35 

tile,  uses  of,  on  earth  roads,  with  table  of  sizes,  35,  36 
Duluth,  street  grades  in,  167,  168 

Dupuit  and  Morin  experiment  on  speed  and  resistance,  9 
Dust,  inorganic,  for  sheet  asphalt  pavement,  250 
Dwellings,  entrances  or  driveways  to,  New  Jersey  practice,  132 
Dynamometer,  self-recording,  used  in  Missouri  road  tests,  7 
Dynograph  described,  with  illustrations,  19,  20 

EARTH  roads,  clay,  treatment  of,  with  illustrations,  41 
construction  of,  26  et  seq. 
ditching  for  various  surfaces,  41,  42 
drainage  as  factor  in  maintenance,  25,  27,  28 
gravel  on,  benefit  of,  53 
maintenance  and  repair,  44,  45 


INDEX  307 

Earth  roads,  Missouri  tests  on,  7,  8 

slope  of,  with  table,  43 

thorough  consideration  of,  24 

use  of  rollers  on,  32 

width  and  right  of  way,  with  illustration,  42 
Earthwork,  excavation,  etc.,  43 

Embankment  in  gravel  roads,  New  Jersey  practice,  57 
Engineer,  selection  and  duties  of,  New  Jersey,  65 
Excavation  in  gravel  roads,  New  Jersey  practice,  57 
Expansion,  allowance  for,  in  wood  pavements,  280,  281 

FAILURE,  causes  of,  in  wood  pavements,  281,  282 
Field  stone  for  road-building,  105 
Filler  for  brick  pavements,  204,  205,  218 
Fillers  for  stone-pavement  joints,  182 
New  York  City  practice,  182 

wood  pavement  joints,  280 
Flagging  for  sheet  asphalt  pavement,  239-242 
Flagstones,  treatment  of,  in  block  asphalt  work,  262,  263 
Foundation  for  brick  pavements,  202,  203,  212 

sheet  asphalt  pavement,  227,  228 

wood  pavement,  279 

France,  treatment  of  trees  in  street  design,  174 
Friction,  axle,  considered,  with  formula,  1,  2 

GOVERNMENT  (U.  S.)  tests  in  traction  resistance,  12,  14-18 
Grade  and  crown  for  sheet  asphalt  pavement,  231,  232 
Baker's  table  showing  effect  of,  on  load,  23 
effect  of,  Massachusetts  Commission  report  on,  21 
of,  on  crown  of,  stone  road,  table,  113 
of,  on  tractive  force,  with  table  and  illustration,  21,  22 
in  wood  pavements,  281 

longitudinal,  as  factor  in  maintenance  of  stone  roads,  117 
resistance,  to  estimate,  20 
Grades  at  street  intersections,  168 

street,  importance  of,  167 
Grading  of  gravel  roads,  50 

gravel  roads,  New  Jersey  practice,  57 
Granite  for  road-building,  105 
Granite-block  pavement,  178-193 

pavement,  kinds  of  stone  used,  179 

size  of  blocks,  179,  180 

pavements,  New  York  City  specifications,  183-193 
pavements,  size  of  blocks,  New  York  City  practice,  190 
cement  for,  190,  191 


308  INDEX 

Gravel,  benefit  of,  on  earth  roads,  53 
roads,  binder,  selection  of,  47 

chert  in  binder,  48 

clay  on,  47 

crown  of,  50 

drainage  of,  49,  50 

general  study  of,  46  et  seq. 

grading  of,  50 

maintenance,  53,  54 

methods  of  construction,  50-53 

Missouri  tests  on,  7 

New  Jersey  practice,  55-69 

repairs  of,  54,  55 

screening  for,  49 

specifications  of  New  Jersey  Commissioner,  55-69 

surface  construction,  50,  51 

trench  construction  of,  52,  53 

vs.  macadam,  comparison,  55 
selection  of,  46  et  seq. 
Grooved  blocks  in  wood  paving,  299 

Gutters  and  curbs  for  city  streets,  with  illustrations,  169-172 
or  side  ditches,  stone  roads,  New  Jersey  practice,  133 

HARRISON,  E.  G.,  report  on  repairs  of  macadam  roads,  114-122 
Haupt,  Lewis  M.,  on  diagonal  system  of  city  streets,  159-164 
Heading  stones  for  sheet  asphalt  pavement,  242 
Herring  and  Rosewater,  plan  of  intersection  grades,  168 

Rudolph,  table  of  effects  of  surface  on  tractive  force,  11,  12 

INORGANIC  dust  for  sheet  asphalt  pavement,  250 
Intersections,  brick,  pavements  with  illustrations,  206-208 

of  streets,  grades  at,  168 
Iowa  State  University  tests  on  brick  and  asphalt  pavements,  12,  13 

JOINTS  in  wood  pavement,  filling  for,  280 
stone  pavements,  fillers  for,  182 

LAYING  sheet  asphalt  pavement,  process  of,  251 
wood  pavement,  279-282 

pavements,  New  York  City  method  of  laying,  298,  299 
Liabilities  of  contractor,  New  Jersey  specifications,  62,  63 
Lifting  of  stone  road,  when  and  how  it  should  be  done,  124 
Limestone  for  road-building,  105 
Liquid  asphalt,  249 
Loads,  comparison  of,  on  various  pavements,  illustration,  196 


INDEX  309 

Loam,  gravelly,  on  earth  roads,  with  illustration,  41 

sandy,  on  earth  roads,  with  illustration.  41 
Location  of  city  streets,  156,  157 
Lots,  size  of,  165 

MACADAM,  his  definition  of  the  road,  with  illustration,  70,  71 

opinion  of  binding  material,  124 

material,  abrasion  machine  for,  described  and  illustrated,  92 
pavement,  Missouri  tests  on,  7 
modern,  74 

New  Jersey  prac^ce,  130 
road,  binding  material  for,  Macadam's  opinion,  124 

effects  of  various  rollings,  111,  112 
roads,  E.  G.  Harrison's  report  on  repairs,  114-122 

vs.  gravel,  comparison,  55 

surface,  excavating  and  preparing  roadbed,  trenching,  illustrated,  106, 107 
Machine,  briquette,  for  stone  tests,  illustrated,  95,  97 

De  Camp,  for  oiling  roads,  described  and  illustrated,  147,  148 
for  testing  brick  for  paving,  199 
old  Deval,  in  abrasion  tests,  91 

road,  grading  the  subgrade  of  stone  road,  illustrated,  75,  77 
Maintenance  of  earth  roads,  44,  45 
gravel  roads,  53,  54 

stone  roads,  longitudinal  grade  as  factor  in  repairs,  117 
stone  roads,  ravelling  as  factor  in,  119,  121,  122 
stone  roads,  ruts  as  factor,  118 
stone  roads,  trash  or  rubbish  as  factor,  120.  121 
Maltha,  when  it  may  be  used,  249 
Manhole,  covers,  heads,  etc.,  184 

Manholes,  catch-basins,  etc.,  in  block  asphalt  job,  256 
Maryland  collects  only  half  tolls  from  drivers  of  broad-tired  vehicles,  7 

shell  roads  in,  150 

Massachusetts  Commission  absorption  test  of  stone,  104 
method  of  stone  cementation  tests,  95,  96 
report  on  effect  of  grade,  21 
reports  on  tire  widths,  6 
experience  in  use  of  trees  on  highway,  175 
practice  in  laying  stone,  110 

in  surfacing  for  stone  roads,  108,  109 
Materials  in  gravel  roads,  New  Jersey  practice,  59 

old,  removal  and  ownership  of,  New  York  City  practice,  184 
patented,  procedure  in  case  of,  272 

McNeill,  Sir  John,  table  of  effects  of  surface  on  tractive  force,  10 
Mill,  ball,  in  stone-dust  preparation  for  briquettes,  described  and  illustrated, 
99,  100 


310  INDEX 

Miscellaneous  roads  described  and  illustrated,  143  et  seq. 

Missouri  Experiment  Station  tests  on  different  road  surfaces,  7-9 

Mixture  for  sheet  asphalt  pavement,  composition  of,  250 

Moh's  scale  for  testing  hardness  of  brick,  198 

Monolithic  walks,  treatment  of,  in  block  asphalt  work,  262 

Monuments,  city,  how  treated  by  contractor  in  New  York  City,  185 

Morin  and  Dupuit  experiment  on  speed  and  resistance,  9 

M.,  experiments  on  diameter  of  wheel,  5 
Mortar  bed  by  car  tracks,  New  York  City,  composition  of,  192 

treatment  of,  192 

NATIONAL  PAVING  BRICK  MANUFACTURERS    ASSOCIATION,  "Directions   for 

Laying,"  etc.,  209-221 
New  Jersey  allows  tax  rebate  to  owners  of  wide-tired  vehicles,  6 

practice  and  specifications  for  gravel  roads,  55-69 

practice  in  surfacing  stone  roads,  109 

practice  in  width  of  stone  road,  112 

specifications  for  stone  roads,  126-142 
New  York  City  specifications  for  granite-block  pavements,  183-193 

City,  street  grades  in,  167 

OIL  for  roads,  quantity  required,  149 

for  roads,  selection  and  application,  146  et  seq. 

petroleum,  tor  asphaltic  cement,  requirements  of,  249 
Oiled  crust,  the  White  smoother,  use  of,  149 

crusts,  various,  for  examination,  146 

roads  described  and  illustrated,  144-149 

De  Camp  machine  for,  described  and  illustrated,  147,  148 

PATCHING  of  stone  roads,  practice  in,  125 
Patented  materials,  procedure  in  case  of,  272 
Pavement,  Belgian-block,  see  Belgian-block  pavement, 

granite-block,  see  Granite-block  pavement 
Pavements,  asphalt,  see  Asphalt  pavements 

brick,  see  Brick  pavements 

cobblestone,  see  Cobblestone  pavements 

stone,  see  Stone  pavements 

various,  comparison  of  loads  carried  on,  196 
effects  of,  on  tractive  force,  illustrated,  10 
labor  required  to  clean,  illustrated,  197 

wood,  see  Wood  pavements 

Payment  for  labor,  materials,  etc.,  New  Jersey,  68 
Penfold  on  repairs  to  stone  roads,  123 
Petroleum  oil  for  asphaltic  cement,  requirements  of,  249 


INDEX  311 

Pittsburg,  street  grades  in,  167 

Plan  and  system  in  city  streets,  with  illustrations  and  formulas,  157-164 

Plank  roads,  construction  of,  152,  153 

Plans  and  drawings  for  gravel  roads,  New  Jersey  practice,  56 

Power  required  to  draw  a  wheel  over  an  obstacle,  diagram,  4 

Preserved  woods,  value  of,  in  wood  pavements,  282 

RAVELLING  as  factor  in  maintenance  on  stone  roads,  119,  121,  122 

Rectangular  system  of  city  streets,  with  illustration,  157,  158 

Repair  of  earth  roads,  44,  45 

Repairs  and  maintenance  of  stone  roads,  114-125 

Resistance,  grade,  to  estimate,  with  formulas,  16 

rolling,  explained,  2 

to  abrasion,  stone  roads,  91-94 
Resistances,  tractive,  considered  at  length,  1  et  seq. 
Roads,  burnt-clay,  described,  143 

charcoal,  construction  of,  151,  152 

coal-slack,  151 

corduroy,  described,  143,  144 

miscellaneous,  described  and  illustrated,  143  et  seq. 

oiling,  described  and  illustrated,  144-149 

plank,  construction  of,  152,  153 

sand-clay,  154,  155 

shale,  varieties  and  value,  150,  151 

slag,  150,  151 

stone,  broken-stone,  see  Stone  roads 
Rock  asphalts,  laying,  252 

requirements  of,  when  used,  251 
Roller,  steam,  on  finished  stone  road,  illustrated,  87 
Rollers,  use  of,  on  earth  roads,  32 
Rolling,  brick  pavements,  218 

in  case  of  block  asphalt  pavement,  258 

stone  roads,  described  and  illustrated,  111,  112 

roads,  New  Jersey  practice,  131 

Rosewater  and  Herring,  plan  of  intersection  grades,  168 
Ruts  as  factor  in  maintenance  of  stone  roads,  118 

prevention  of,  by  arrangement  of  axle-trees  and  wheels,  118,  119 

SAND  for  sheet  asphalt  pavement,  229,  242 
Sand-clay  roads,  154,  155 
Sandstone  for  road-building,  105 
Screening  for  gravel  roads,  49 
Shale  in  road-building,  105 

roads,  varieties  and  value,  150,  151 
Sheet  asphalt  pavement,  see  Asphalt  pavement,  sheet 


312  INDEX 

Shoulder  in  gravel  roads,  New  Jersey  practice,  58 

Side-hill  streets,  treatment  of,  169 

Sidewalks  for  gravel  roads,  New  Jersey  practice,  60 

New  York  City  practice,  187 

Sieves  and  screens  for  stone  cementation  tests,  98,  99 
Size  of  broken  stone  for  roads,  109,  110 
Slag  roads,  150,  151 
Slope  in  gravel  roads,  New  Jersey  practice,  58 

earth  roads,  with  table,  43 
Specifications,  New  Jersey,  for  stone  roads,  126-142 

New  York  City,  for  block  asphalt  pavements,  254-272 
New  York  City,  for  sheet  asphalt  pavement,  233-253 
Speed,  relation  of,  to  rolling  resistance,  9 
Springs  beneficial  to  road  and  vehicle,  9 
Stone  breaker,  for  sheet  asphalt  pavement,  242,  243 

placing  on  prepared  subgrade,  illustrated,  79 
cementation  tests,  Washington  practice,  101 
dust  for  cementation  test,  preparing,  98 

for  sheet  asphalt  pavement,  229 

for  road,  qualities  required,  opinions  of  Prof.  A.  Black,  81-91 
roadmaking,  qualities  of,  table,  103 
roads,  absorption  test  of  Massachusetts  Commission,  104 
French  tests  and  coefficient  of  wear,  93 
laying,  Massachusetts  practice,  110 
pavements,  176  et  seq. 

bridgestones  for,  243,  244 
cement  for,  New  York  City  practice,  191 
fillers  for  joints,  182 
foundation  for,  181 

foundation,  New  York  City  practice,  184 
laying  the  stone,  182 

New  York  City  practice  as  to  manholes,  184 
removing  old  material,  New  York  City  practice,  184 
resistance  to  crushing,  determination  of,  102 
road,  complete,  illustrated,  89 

subgrades  being  covered  with  broken  stone,  illustrated,  79 
roads,  binder  material,  112 

bridges,  etc.,  for,  New  Jersey  requirements,  138 
causes  of  repairing  considered  in  detail,  115-122 
cementation  tests  of  material,  94-102 
cross-section,  113 
crown,  amount  of,  113 

drainage,  New  Jersey  requirements,  133,  137 
forms  of  construction  illustrated,  106,  107 
kinds  of  rock  commonly  used,  104,  105 


INDEX  313 

Stone  roads,  lifting  of,  when  and  how  it  should  be  done,  124 
longitudinal  grade  as  factor  in  maintenance,  117 
maintenance  and  repairs,  Massachusetts  practice,  114 
modern,  practice  in,  73,  74 
New  Jersey  practice  in  covering,  109 
New  Jersey  specifications,  126-142 
patching  of,  practice,  125 
Penfold  on  repairs,  123 

ravelling  as  factor  in  maintenance,  119,  121,  122 
repairs  and  maintenance,  114-125 
resistance  to  abrasion,  tests,  91-94 
ruts  as  factor  in  repairs,  118 
size  of  broken  stone,  109,  110 
thickness  of  covering,  107-110 
width  of,  Massachusetts  practice,  112 
width  of,  New  Jersey  practice,  112 
tests,  method  of  Prof.  A.  Black,  81-91 
toughness  tests,  102 

Street  design,  detailed  study  of,  with  illustrations,  156  et  seq. 
drainage,  169-172 

grades,  importance  and  treatment,  167 
intersections,  grades  at,  168 
Streets,  design,  location,  etc.,  with  illustrations,  156  et  seq. 

diagonal  system,  Haupt  on,  with  illustrations  and  formulas,  159-164 
diagram  of,  in  Washington,  D.  C.,  163 
gutters  and  curbs  for,  with  illustrations,  169-172 
location  of,  156,  157 

plan  and  system  in,  with  illustrations  and  formulas,  157-164 
rectangular  system,  with  illustration,  157,  158 
side-hill,  treatment  of,  169 
treatment  of  crown,  172 
trees  as  factor  in  design,  174,  175 
width  of  carriageway,  165,  166 

Subfoundation  of  gravel  roads,  New  Jersey  practice,  58 
Subgrade  of  stone  road  being  graded  and  rolled  by  machine,  illustrated,  75, 

77 

Subletting  of  contract,  New  Jersey,  67 
Subsurface  drainage  on  earth  roads,  32-38 
Surface,  as  factor  in  resistance  and  tractive  force,  10 

construction  of  gravel  roads,  50,  51 
Surfaces,  road,  Missouri  tests  of  various,  7-9 
Surfacing  for  stone  roads,  Massachusetts  practice,  108,  109 

TELFORD  foundation,  laying,  illustrated,  83 
New  Jersey  practice,  129 


314  INDEX 

Telford  pavement,  description  of,  with  illustrations,  71-74 
modern,  74 

road  construction,  illustrated,  85 
Temperature  of  paving  cement,  246 

paving  cement,  New  York  City  practice,  191 
Tests  of  road  stone,  method  of  Prof.  A.  Black,  81-91 
Tile  drains,  use  of,  on  earth  roads,  with  table  of  sizes,  35,  36 
Tillson  on  making  of  paving  brick,  195,  196 
Tire,  width  of,  effect  on  haulage  and  road  preservation,  6-9 
Tires,  broad,  in  New  Jersey  gravel  road  construction,  61 
in  stone-road  making,  New  Jersey  practice,  134 
Toothing  cement,  246 
Topography  of  city  streets,  156,  157 
Toughness,  tests  of  brick  for  paving,  198-200 

of  stone,  102 
Trackway,  in  Murray  Street,  New  York,  154 

in  Chicago,  154 

the  Albany  and  Schenectady,  154 
Trackways,  abroad  and  in  United  States,  153,  154 

cost  of,  153 

mode  of  construction,  153 

Traction  tests,  findings  of  various  investigators,  10-19 
Tractive  force,  diagram  and  equations  demonstrating,  3,  4 
effect  of  grade  on,  with  table  and  illustrations,  21 
Tractograph,  description  of,  16 

in  pavement  tests,  with  illustration,  16 
Trap  rock  for  roads,  104 

Trash  or  rubbish  on  stone  roads  as  factor  in  maintenance,  120,  121 
Trees,  consideration  of,  in  street  design,  174,  175 

on  highway,  Massachusetts  experience,  175 

varieties  planted,  175 

Trench  construction  of  gravel  roads,  52,  53 
Trenching  stone  road,  illustrated,  106,  107 

UNDERDRAINS  in  gravel  roads,  New  Jersey  practice,  59 

WASHINGTON,  D.  C.,  diagram  or  arrangement  of  streets,  163 
Wear  of  stone,  French  tests  and  coefficient,  93 
Wearing  surface  for  sheet  asphalt  pavement,  229-231 
Weather  considerations  in  New  Jersey  specifications,  138 
Wheel,  diameter  of,  as  affecting  rolling  resistance,  5 
Wheels  and  axle-trees,  arrangement  of,  to  prevent  ruts,  118,  119 
White  smoother,  the,  for  oiled  crust,  use  of,  149 
Width  of  earth  roads,  right  of  way,  etc.,  with  illustrations,  42 
stone  road,  Massachusetts  practice,  112 


INDEX  315 


Wood  pavement,  advantages  and  disadvantages,  274,  275 

allowance  for  expansion  in,  280,  281 

chemical  treatment  of  blocks,  278 

filling  for  joints,  280 

foundation  for,  279 

laying,  279-282 

New  York  City  requirements  in  block  material,  292 

New  York  City  specifications  for,  282-302 
pavements,  causes  of  failure  in,  281,  282 

cement  for,  New  York  City  requirements,  295 

concrete  for,  New  York  City  requirements,  296,  297 

cutting  closures  in,  299 

forms  of  blocks,  277,  278 

grooved  blocks,  299 

method  of  laying,  298,  299 

modern,  history  and  description,  273  et  seq. 

treatment  of  grade  in,  281 

use  of,  in  Europe,  273 

value  of  preserved  woods,  282 

varieties  and  choice  of  woods,  276,  277 
Workmen,  competency  of,  New  Jersey,  66 


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